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Works Cited

• Colten, Harvey R. “Extent and Health Consequences of Chronic Sleep Loss and Sleep Disorders—Sleep Disorders and Sleep Deprivation.” National Center for Biotechnology Information . U.S. National Library of Medicine, 01 Jan. 1970. Web. 03 Nov. 2016. .
• “Dangers of Getting Too Little Sleep.” HealthCommunities . N.p., n.d. Web. 03 Nov. 2016. .
• “Chronic Insomnia’s Dangerous Side-Effects.” Newsweek . Newsweek, 23 Aug. 2009. Web. 03 Nov. 2016. .
• “Chronic Insomnia Linked to Increased Risk of Death.” Mercola.com . N.p., n.d. Web. 03 Nov. 2016. .

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Insomnia: Symptoms, Causes, and Treatments

What it is and how to help you get back your restful nights

Staff Writer

Eric Suni has over a decade of experience as a science writer and was previously an information specialist for the National Cancer Institute.

Want to read more about all our experts in the field?

Dr. Anis Rehman

Internal Medicine Physician

Dr. Rehman, M.D., is a board-certified physician in Internal Medicine as well as Endocrinology, Diabetes, and Metabolism.

Sleep Foundation

Fact-Checking: Our Process

The Sleep Foundation editorial team is dedicated to providing content that meets the highest standards for accuracy and objectivity. Our editors and medical experts rigorously evaluate every article and guide to ensure the information is factual, up-to-date, and free of bias.

The Sleep Foundation fact-checking guidelines are as follows:

• We only cite reputable sources when researching our guides and articles. These include peer-reviewed journals, government reports, academic and medical associations, and interviews with credentialed medical experts and practitioners.
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Table of Contents

What Is Insomnia? 

Symptoms of insomnia, what causes insomnia , how is insomnia diagnosed , treatments for insomnia .

• Insomnia is defined as difficulty either falling or staying asleep that is accompanied by daytime impairments.
• Nighttime insomnia symptoms can include trouble sleeping and early waking.
• Daytime insomnia symptoms may include fatigue, impaired memory, and irritability.
• There is no single established cause of insomnia, and insomnia disorders can often occur alongside other health conditions.

Insomnia is one of the most common health concerns among adults. Insomnia causes sleep issues that interfere with daily life and can be debilitating for some people. Many factors may contribute to insomnia, including stress, medications, and an individual’s sleep habits and environment. 

Insomnia is a sleep disorder characterized by difficulty falling asleep, staying asleep, or both, even if you have ample time and a bedroom environment conducive to restful sleep. An insomnia diagnosis requires these sleep troubles to also cause daytime impairments, such as sleepiness or difficulty concentrating.

Up to two-thirds of people occasionally experience insomnia symptoms . These bouts of sleeplessness may or may not meet the criteria for a formal diagnosis of insomnia, depending on how long they last and whether they cause distress or interfere with daily functioning. But it is important for anyone who has concerns about their sleep to discuss them with a health professional for proper diagnosis and treatment.

A doctor can ask questions to better understand your situation and order tests to determine if an insomnia diagnosis is appropriate. Symptoms of insomnia can overlap with symptoms of other sleep disorders, so it is important to work with a professional rather than attempting to self-diagnose.

Insomnia that goes untreated, leading to long-term sleep deprivation, is linked with a number of harmful effects Trusted Source UpToDate More than 2 million healthcare providers around the world choose UpToDate to help make appropriate care decisions and drive better health outcomes. UpToDate delivers evidence-based clinical decision support that is clear, actionable, and rich with real-world insights. View Source , including lower quality of life and increased risk for substance abuse, chronic pain , heart disease , and diabetes .

Types of Insomnia

The two main types of insomnia are acute insomnia and chronic insomnia. Acute insomnia describes sleep difficulties that last for a few days or weeks, but not longer than three months. Short-term insomnia can often be traced to an external cause or life stressor like divorce, the death of a loved one, or a major illness. If acute insomnia persists over multiple months, it becomes classified as chronic insomnia.

Chronic insomnia is when a person experiences sleeping difficulties and related daytime symptoms, like sleepiness and attention issues, at least three days per week for longer than three months. It is estimated that about 10% to 15% of people have chronic insomnia.

People with chronic insomnia commonly feel distressed about their inability to sleep and the daytime symptoms caused by those sleep issues. Symptoms are generally severe enough to affect a person’s work or school performance as well as their social or family life.

Are You Getting Enough Deep Sleep?

A variety of issues can cause degrade your sleep quality. Answer three questions to understand if it’s a concern you should worry about.

The symptoms of insomnia include various sleep-related difficulties and daytime problems. Common sleep issues that can signal the presence of insomnia include:

• Trouble falling asleep
• Trouble staying asleep throughout the night
• Unwanted early morning waking
• Resisting sleeping at bedtime in children and teens
• Difficulty sleeping without a caregiver’s help in children and teens

In addition, insomnia causes daytime symptoms related to sleep loss. Those with insomnia often report feeling fatigued during waking hours, which may lead to impaired attention or memory. Insomnia-related sleepiness can affect work, school or social performance, and increase the risk of accidents. Insomnia has the potential to negatively influence behavioral health and may contribute to instances of irritability, hyperactivity, or aggressiveness, especially in children.

There is no main cause of insomnia . However, research suggests that in many people insomnia likely results from certain types of physiological arousal at unwanted times, disrupting normal patterns of sleep. Examples of such arousal can include a heightened heart rate, a higher body temperature, and increased levels of specific hormones, like cortisol.

A person’s family history , age , and gender may also play a role in their susceptibility to insomnia. Additionally, insomnia disorders often occur alongside mental health disorders , including depression and anxiety . It is believed that the cause of insomnia may be distinct in people who have both insomnia and mental health conditions.

Risk Factors for Insomnia

While there is no single cause of insomnia, studies have identified factors that can put a person at a greater risk for experiencing insomnia Trusted Source American Academy of Sleep Medicine (AASM) AASM sets standards and promotes excellence in sleep medicine health care, education, and research. View Source . These include, but are not limited to:

• Being a woman or assigned female at birth
• Lower socioeconomic status
• Medical conditions like diabetes and chronic pain
• Other sleep disorders such as restless legs syndrome and sleep apnea
• Mood disorders including depression and anxiety Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source  
• Having an immediate family member with insomnia

It is important to note that not everyone who has one or more of these risk factors will have insomnia, and not everyone with insomnia will have one of these risk factors.

Doctors generally diagnose insomnia by evaluating a person’s sleep habits and medical history. 

Typically, a patient’s description of their symptoms informs their insomnia diagnosis. A doctor may instruct patients to keep a sleep diary for a week or more, which can provide insight about a person’s sleep duration, perceived sleep quality, and lifestyle choices that may contribute to sleep problems. Other self-reporting diagnostic tools, including the Pittsburgh Sleep Quality Index, may be used by medical professionals in a clinical setting to determine the severity of insomnia symptoms.  

If a doctor needs to rule out other sleep disorders that could be causing a person’s symptoms, other assessments, such as a sleep study , may be ordered.

Treatment for insomnia depends on how long a person has been experiencing sleep issues and any specific factors that are contributing to their sleep loss. If insomnia is associated with another condition, such as sleep apnea or depression, treatment of the other condition often improves sleep.

It is important to get help with insomnia sooner than later. For people with short-term insomnia, care may be focused on discussing practices to support sleep hygiene . Temporary use of a prescription sleep aid may be an option if the insomnia is causing high levels of concern or distress. 

A few treatment approaches are available for people with insomnia that persists for weeks or months.

Cognitive Behavioral Therapy for Insomnia (CBT-I)

Experts consider cognitive behavioral therapy for insomnia (CBT-I) to be the most effective initial treatment for chronic insomnia. CBT-I helps people manage anxiety they feel about their sleep issues and establish better sleep habits.

Sleep Medications

If a person experiences significant symptoms from insomnia, or in cases where CBT-I does not help, medication may be recommended. Medication can help promote sleep but may also come with side effects , such as daytime drowsiness or confusion.

Homeopathic Treatments 

Some people with insomnia may be interested in exploring other options, such as melatonin or dietary supplements, yoga , hypnosis , or aromatherapy . However, scientific evidence supporting the use of these methods to treat insomnia is lacking at this time Trusted Source National Center for Complementary and Integrative Health (NICCH) NCCIH funds and conducts research to help answer important scientific and public health questions about complementary health approaches. View Source .

Lifestyle Changes

Maintaining healthy sleep habits after insomnia treatment may help keep insomnia from returning Trusted Source Medline Plus MedlinePlus is an online health information resource for patients and their families and friends. View Source . 

• Set a sleep schedule: Maintain the same bedtime and wake time every day, even on weekends.
• Establish a dedicated sleep space: Reserve use of the bed for only sex and sleep.
• Be mindful of substance use: Curb consumption of caffeine , alcohol , or nicotine, especially near bedtime
• Control light exposure: Try to keep the bedroom both dark and quiet, and refrain from watching television or using other electronics that emit blue light before bed. 
• Keep sleep-related anxiety in check: If you are experiencing anxiety about sleep troubles, get out of bed and try a relaxing activity like reading, taking a bath, or meditating. 
• Adjust your eating habits: Avoid eating large meals too close to bedtime.
• When Your Partner Snores, No One Sleeps
• Can the Rise of Chronoworking Help Fix Our Sleep?
• Streamlining Cognitive Behavioral Therapy for Chronic Insomnia
• Blood-based Marker Developed to Identify Sleep Deprivation

About Our Editorial Team

Eric Suni, Staff Writer

Medically Reviewed by

Dr. Anis Rehman, Internal Medicine Physician MD

References 6 sources.

Bonnet, M., & Arand, D. (2022, April 15). Risk factors, comorbidities, and consequences of insomnia in adults. In R. Benca (Ed.). UpToDate., Retrieved June 5, 2023, from

American Academy of Sleep Medicine. (2014). The International Classification of Sleep Disorders – Third Edition (ICSD-3). Darien, IL.

Bjorøy, I., Jørgensen, V. A., Pallesen, S., & Bjorvatn, B. (2020). The prevalence of insomnia subtypes in relation to demographic characteristics, anxiety, depression, alcohol consumption and use of hypnotics. Frontiers in Psychology, 11, 527.

Bonnet, M. H., & Arand, D. L. (2021, June 18). Evaluation and diagnosis of insomnia in adults. In R. Benca (Ed.). UpToDate., Retrieved June 5, 2023, from

National Center for Complementary and Integrative Health. (2015, September). Sleep disorders: In depth., Retrieved June 5, 2023, from

A.D.A.M. Medical Encyclopedia. (2022, May 12). Changing your sleep habits. MedlinePlus., Retrieved June 5, 2023, from

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Publication

Insomnia Overview: Epidemiology, Pathophysiology, Diagnosis and Monitoring, and Nonpharmacologic Therapy

Am J Manag Care . 2020;26:S76-S84. https://doi.org/10.37765/ajmc.2020.42769

Insomnia, whether short-term or chronic, is a common condition. It has a negative impact on vulnerable patient groups, including active military personnel and veterans, patients with coexisting psychiatric and medical disorders, those in life transitions such as menopause, and elderly persons. Although cognitive behavioral therapy for insomnia (CBTI) is first-line treatment for insomnia, its high cost and a lack of trained providers has prevented widespread uptake. Now, digital CBTI (dCBTI) is emerging as a scalable option with the potential to overcome these barriers in managed care. The first part of this article reviews the epidemiology and pathophysiology of insomnia with a focus on vulnerable patient groups. The second part explores the rapidly evolving landscape of nondrug therapy for insomnia. The underlying concepts and supporting evidence for CBTI and dCBTI are presented, including their utility in vulnerable patient groups. Introduction

Insomnia, the most common sleep disorder, is a substantial burden for the US healthcare system and vulnerable patient groups. 1 Combined direct and indirect costs for insomnia in the United States exceed $100 billion annually. 2 Because it is so common, the annual loss of quality-adjusted life-years from insomnia appears to be greater than the loss from other medical and psychiatric conditions, including arthritis, depression, and hypertension. 3 Between 1993 and 2015, the diagnosis of insomnia during office visits in the United States increased 11-fold, from 800,000 to 9.4 million. 4 Further, insomnia is linked to higher healthcare utilization and costs, especially in patients with coexisting medical or psychiatric disorders, 5,6 illustrating why it is an important managed care issue. In a recent study of a managed care population, an 80% increase in healthcare costs after a diagnosis of insomnia was attributed to management of insomnia and coexisting conditions. 7

Insomnia: Classification, Diagnosis, and Monitoring

In 2014, the third edition of the International Classification of Sleep Disorders ( ICSD-3 ), the most widely used classification system for sleep disorders, revised how insomnia is defined. 8 It now subclassifies insomnia as short-term, chronic, or other. The previous subclassification of chronic insomnia as primary or comorbid was eliminated because it did not improve diagnostic accuracy or differentiate treatment options. The underlying rationale for removal was that calling insomnia comorbid may misleadingly imply that it is a secondary concern that will resolve with adequate treatment of the comorbid condition. To the contrary, the maladaptive cognitions and behaviors that perpetuate insomnia must be addressed regardless of coexisting medical or psychiatric disorders. 8

Diagnostic criteria for insomnia include difficulty getting to sleep or staying asleep and results in daytime dysfunction in a patient who has an adequate opportunity to sleep. 8 It is short-term if symptoms occur for less than 3 months and chronic if symptoms occur 3 or more times per week for 3 months or longer. Insomnia is often precipitated by a significant life stressor (eg, acute pain, traumatic event). It may end when the stressor resolves or the patient learns to cope, or it may evolve into chronic insomnia. 9 Short-term and chronic insomnia may be inferred from a patient’s language. No longer mentioning a precipitating life stressor and talking about insomnia as “the problem” may mark the transition from short-term to chronic insomnia. 9

Chronic insomnia is a clinical diagnosis that relies heavily on patient history about sleep, medical and psychiatric conditions, and substance use. 10 The sleep history should characterize how sleep is disturbed and document the daytime consequences of insomnia. Descriptors that measure and characterize sleep disturbances are shown in Table 1 . 11-16 When patients report complaints of excessive daytime sleepiness, a diagnosis of a hypersomnolence disorder, narcolepsy, or a sleep-related breathing disorder should be considered. 17 The Epworth Sleepiness Scale (ESS) can be used to differentiate between fatigue and significant daytime sleepiness that indicates the potential for another sleep disorder. 16 Questionnaires, such as the Insomnia Severity Index (ISI) and Dysfunctional Beliefs and Attitudes About Sleep scale, and sleep diaries, such as the Consensus Sleep Diary, are useful to identify behaviors that perpetuate insomnia and to monitor treatment effects (see Table 1 11-16 ). 12-14 A general questionnaire can identify comorbidities that contribute to insomnia or affect its management. 10 A medication and substance use history, including over-the-counter drugs and dietary supplements, identifies drugs and substances that interfere with sleep.

Insomnia can occur as a primary sleep disorder, a symptom of another sleep disorder (eg, obstructive sleep apnea [OSA], restless legs syndrome [RLS]), periodic leg movements during sleep [PLMS]), or a comorbid sleep disorder. 8,16,18 An estimated 39% to 55% of patients already diagnosed with OSA or sleep disordered breathing have reported symptoms of insomnia. 19 Conversely, approximately 30% of elderly patients already diagnosed with insomnia have been found to have moderate OSA based on an apnea-hypopnea index of 15 or greater. 19 In a large cross-sectional survey, almost 30% of participants with insomnia reported having RLS symptoms 3 or more nights per week, and 85% to 95% of patients with RLS also have PLMS. 18,20

The sleep history may suggest the presence of another sleep disorder. For example, snoring or breathing pauses suggest OSA, whereas a sleeping partner getting kicked during the night suggests RLS and/or PLMS. Concerns about OSA should be heightened in patients with obesity or a thick neck. 16 Because symptoms of RLS can be difficult for patients to describe, it may help to ask about symptoms that involuntarily make them want to move their legs, improve by moving, and worsen at night. 21 Polysomnography is not necessary for the diagnosis of chronic insomnia, but it is indicated if another sleep disorder is suspected. As part of the Choose Wisely initiative, the American Academy of Sleep Medicine (AASM) recommends against polysomnography in patients with chronic insomnia unless symptoms suggest a comorbid sleep disorder (eg, OSA, RLS, PLMS). 22

Pathophysiology of Insomnia

Insomnia is a complex interaction of psychological cognitive arousal and altered circadian and homeostatic mechanisms. Decreased function of the sleep-wake switch may also contribute to insomnia. During sleep, there is a slow transition through stages of non—rapid-eye movement (non-REM) sleep to cycles of rapid-eye movement (REM) sleep. 23 The AASM classifies sleep into 5 progressive stages 23 :

• Stage W (wakefulness)
• Stage N1 (relaxed wakefulness)
• Stage N2 (light sleep)
• Stage N3 (deep or slow-wave sleep)
• Stage R (REM sleep or dreaming)

Stages N1-N3 are phases of non-REM sleep in which cortical activity is low, whereas the brain is highly active during REM sleep. 23

Multiple brain centers work in concert to promote sleep or wakefulness. The sleep-wake cycle is a complex process in which wakefulness and sleep are switched on and off by reciprocal systems in a feedback loop. 23,24 Wakefulness results from ascending activity in a number of brainstem and posterior hypothalamic nuclei in what is referred to as the ascending reticular activation system (ARAS). This system projects widely into the cerebral cortex. Hypocretin/orexin-containing neurons in the lateral hypothalamus (orexin) project to hypothalamic and brainstem arousal centers and functionally reinforce their activity during wakefulness.

This model of the sleep-wake cycle is often called the flip-flop switch because it permits one to either be awake or asleep, but not both, at the same time. Via the switching mechanism, the active state suppresses the other state until circadian rhythms induce a switch to the reciprocal state. The cerebral cortex and the limbic system further modify wakefulness. Sleep-promoting centers in the anterior hypothalamus project into the brainstem and posterior arousal centers and function with the lateral hypothalamus as a sleep-wake switch.

Circadian factors promote wakefulness on a roughly 24-hour biological clock, whereas homeostatic factors respond to accumulated wakefulness with the drive for sleep. 11 In the brain, the ARAS promotes wakefulness and the ventrolateral preoptic region (VLPR) promotes sleep. During wakefulness, the ARAS inhibits the VLPR via activation of cholinergic neurons, monoaminergic cell bundles, and orexin nuclei in the lateral hypothalamus. The orexin system promotes wakefulness and alertness and works to balance sleep and wakefulness. Orexin system activation maintains the fully awake state for longer periods of time; conversely, deactivation of the orexin system allows for consolidated sleep during the night. Orexinergic signaling by 2 distinct forms, orexin A and orexin B, maintains wakefulness via continuous depolarization in wake-promoting brain nuclei. Sleep is cued by a homeostatic sleep drive inhibition of orexins. During sleep, the ventrolateral preoptic nucleus inhibits the ARAS via 2 inhibitory neurotransmitters, γ-aminobutyric acid (GABA) and galanin. 23,24 GABA is the neurotransmitter that most widely promotes sleep, whereas norepinephrine and dopamine promote wakefulness; serotonin is necessary for both optimal sleep and wakefulness. 23,24 Flip-flop switching also regulates the transition from non-REM to REM sleep. 25 Within regions of the brainstem, REM-off and REM-on areas inhibit each other. 25

The 3P behavioral model of insomnia helps to explain how acute insomnia becomes chronic and lays the groundwork for assessing insomnia in individual patients. 26 The 3Ps, which occur in temporal order, are factors that:

• Predispose an individual to insomnia
• Precipitate an acute episode of insomnia
• Perpetuate insomnia from acute to chronic

Predisposing factors, which are generally not modifiable, include genetics and personality traits (eg, being a worrier; family history of poor sleep) that lead to physiologic and cognitive hyperarousal. As shown in Table 2 , 27-33 precipitating factors that trigger insomnia are typically stressful life events. Patients usually identify problems related to health, family, work, or school as precipitating factors for insomnia. 34 Perpetuating factors are the maladaptive behaviors, thoughts, and coping strategies that allow insomnia to continue after original triggers have resolved. 35 Physical examples of maladaptive behaviors include daytime napping or spending too much time in bed. Less quantifiable perpetuators include dysfunctional beliefs, expectations, and attributions about sleep as well as an intense desire to solve the sleep problem.

Insomnia Burden: Epidemiology and Vulnerable Patient Groups

The burden of insomnia in the United States was extensively characterized in 2008-2009 by the American Insomnia Survey, a nationwide survey of more than 10,000 members in a national health plan. 36-38 More than one-half of adults had difficulty sleeping, and 22.1% met Diagnostic and Statistical Manual of Mental Disorders, 4th Edition diagnostic criteria for insomnia. The prevalence of insomnia based on other diagnostic criteria in place at the time was 14.7% for ICSD-2 and 3.9% for International Statistical Classification of Diseases and Related Health Problems, 10th Revision . 36 The most prevalent symptom was difficulty maintaining sleep (61%), followed by early morning awakening (2.2%), difficulty initiating sleep (7.7%), and nonrestorative sleep (25.2%). 38 Although the overall prevalence of insomnia in working people was 23.2%, it was significantly higher in women than men (27.1% vs 19.7%; P = .001). 37 The higher prevalence of insomnia in women begins in adolescence, and it is especially high during menopause. 32 In addition to women, insomnia has higher prevalence in the elderly population, individuals with low socioeconomic status, and those with poor health or low quality of life (QOL). 39,40 As shown in Table 2, 27-33 many social or societal stressors are associated with insomnia. For example, results of a recent study showed the incidence of insomnia in homeless people was twice that of the general population (41% vs 19%). 31

Approximately 30% to 40% of adults in the United States report symptoms of insomnia at some point in a given year. 17 Short-term insomnia has an estimated prevalence of 9.5% in the United States, but about 1 in 5 cases of short-term insomnia transitions to chronic insomnia, which can persist for years. 41 In longitudinal studies, insomnia continued in 40% to 70% of patients for as long as 4 years. 42-44 Although symptoms persist in some patients, insomnia may have a waxing and waning course in others. 44

The incidence of insomnia appears to be increasing in the United States. 45 Based on National Health Interview Survey data, the unadjusted prevalence of insomnia or trouble sleeping increased by 8% over a decade, from 17.5% (37.5 million adults) in 2002 to 19.2% (46.2 million adults) in 2012. 45 National Ambulatory Medical Care Survey data showed that the number of office visits for insomnia increased by 13% over 10 years, from 4.9 million visits in 1999 to 5.5 million visits in 2010. 46 Based on Medicare data, physician-diagnosed insomnia increased from 3.9% in 2006 to 6.2% in 2013. 47 An increase in insomnia has also been noted in Canada, where data collected with similar methodology showed an increase in adults with insomnia symptoms from 13.4% in 2002 to 23.8% in 2015. 39

Insufficient sleep has been linked to poor outcomes across many disease states, including cardiovascular and cerebrovascular disease, cancer, hypertension, and diabetes. 48 Epidemiologic studies have linked insomnia symptoms to the development of other diseases, including type 2 diabetes (hazard ratio [HR], 1.28; 95% CI, 1.24-1.33), dementia (relative risk, 1.53; 95% CI, 1.07-2.18), stroke (HR, 1.54; 95% CI, 1.38-1.72), and chronic kidney disease (HR, 1.39; 95% CI, 1.34-1.44). 49-52 Specific symptoms of insomnia have been linked to an increase in total cardiovascular disease (CVD) incidence. 53 Respective HRs for increased risk of total CVD incidence for difficulty initiating or maintaining sleep, early morning awakening, and daytime dysfunction were 1.09 (95% CI, 1.07-1.11), 1.07 (95% CI, 1.05-1.09), and 1.13 (95% CI, 1.09-1.18). 53 The most recent evidence does not indicate a link between insomnia and mortality, 54 although insomnia is also linked to higher rates of workplace injuries and traffic accidents. 37,55

Vulnerable Patient Groups

Insomnia has bidirectional effects with coexisting medical and mental disorders, especially depression. 17 Insomnia is a significant predictor for subsequent onset of psychiatric disorders, including depression (odds ratio [OR], 2.83; 95% CI, 1.55-5.17), anxiety (OR, 3.23; 95% CI, 1.52-6.85), and alcohol abuse (OR, 1.35; 95% CI, 1.08-1.67). 56

Military Personnel and Veterans

Active military personnel and veterans are extremely vulnerable to insomnia. Most veterans report sleep disturbances and about half meet the diagnosis of insomnia. 57,58 Since 2001, when the longest overseas conflict in US history began, insomnia in military service members has skyrocketed and has been linked to deployment and combat exposure. In a retrospective cohort study of more than 1.3 million active duty US Army soldiers, the incidence of insomnia increased by 652% between 2003 and 2011. 59 Comorbid conditions with a 2- or 3-fold higher risk of insomnia included sleep-related movement disorders, posttraumatic stress disorder (PTSD), anxiety, adjustment reaction, and acute reaction to stress. The incidence of OSA also increased by 600% over this period. Medical conditions linked to more than a 2-fold risk of OSA included hypertension, gastroesophageal reflux, diabetes, PTSD, and being overweight or obese. 59 More than 90% of veterans with PTSD report sleep disturbances, primarily insomnia and nightmares. 60 The current thinking is that insomnia helps drive the suicide epidemic in veterans by exacerbating depression and PTSD. 61,62 Suicide prevention is part of the rationale for a Veterans Affairs public health campaign that offers CBTI. 63

Traumatic Brain Injury

Almost 2.9 million traumatic brain injury (TBI)-related emergency department visits, hospitalizations, and deaths occurred in the United States in 2014. 64 Insomnia occurs in 30% to 65% of patients with chronic TBI symptoms. 65 In patients with mild TBI, insomnia appears to have a relationship with other TBI complications, including PTSD, depression, and chronic pain. 65 A recent longitudinal study correlated the impact of sleep disturbances on functional impairment in adults with mild TBI. 66 Functional impairment was highest among those with both insomnia and short sleep (43%-79%), followed by insomnia alone (33%-64%), those with short sleep of less than 6 hours (29%-33%), and good sleepers (15%-25%). The relationship between sleep quality and global functioning was also bidirectional, with greater sleep disturbance predicting greater functional impairment months later and vice versa. This raises the possibility that early detection and management of sleep disturbances may both identify patients with a poor prognosis and improve recovery from TBI. 66

Depression and Anxiety Disorders

A key concern for clinicians is that insomnia strongly predicts the occurrence of depression. About 90% of patients with major depressive disorder (MDD) report difficulty sleeping. 67 Although sleep disturbances are part of the diagnostic criteria for MDD and generalized anxiety disorder, insomnia also occurs as a coexisting disorder that worsens the mood disorder prognosis. 17 In one of the earliest studies to investigate the relationship between insomnia and psychiatric disorders, 40% of patients with insomnia had a psychiatric disorder, most commonly an anxiety disorder (24%) or depression (14%). 68 In this study, people with insomnia had a substantial risk of developing depression over the following year (OR, 39.8; 95% CI, 19.8-80.0). The risk of developing an anxiety disorder was also increased (OR, 6.3; 95% CI, 3.6-10.9). 68 Results of a meta-analysis of 34 prospective cohort studies found that insomnia more than doubled the risk of developing depression. 69 This is supported by new evidence from the Sequenced Treatment Alternatives to Relieve Depression trial in which improvements in sleep occurred independently from MDD remission. 67 Insomnia increases the risk of suicide in depressed patients (OR, 2.29; 95% CI, 1.69-3.10), 70 and persistent insomnia also increases the risk of depression relapse. 10

Alcohol and Substance Use

Alcohol use and insomnia have a complex relationship. The prevalence of insomnia in alcohol dependence is estimated at 36% to 91%. 71 Chronic insomnia increases the risk of relapse in alcoholism. 10 Approximately 15% to 30% of people report drinking to manage insomnia, 32,72 and because people can rapidly develop tolerance to the sedative effects of alcohol, self-treating insomnia with alcohol has been proposed as a gateway to problem drinking. 72 A similar theme has been suggested for cannabis in that initial improvements in sleep may be followed by tolerance. 73 Daily cannabis users report high rates of sleep disturbances, given that a tolerance often develops to the sleep-inducing effects of cannabis. Further, cannabis withdrawal can cause severe insomnia characterized by trouble falling asleep and staying asleep, as well as vivid dreams, all of which make it difficult to quit. 73

Menopause and Aging

Vasomotor symptoms are an important precipitating factor for chronic insomnia in peri- and postmenopausal women. In a cross-sectional study, the prevalence of chronic insomnia symptoms increased with the severity of vasomotor symptoms, reaching greater than 80% in women with severe vasomotor symptoms. 74 Similar to other scenarios, insomnia and depression appear to have a bidirectional relationship in perimenopausal women, with insomnia contributing to depressive symptoms and vice versa. 75

In a longitudinal study of community-living persons aged in their mid-80s with a burden of medical conditions and taking multiple medications, the prevalence of insomnia was 43% 76 ; however, the mean ISI score was 12.3, suggesting mild severity. Insomnia was associated with depressive symptoms (OR, 8.34; 95% CI, 4.49-15.47) and RLS (OR, 2.49; 95% CI, 1.48-4.21). Biological factors related to aging that are thought to predispose elderly persons to insomnia include circadian rhythm changes that lead to less deep sleep, more sleep fragmentation, and early morning awakening. 77 Precipitating factors may include an increasing burden of health problems with sleep-disruptive symptoms (eg, nocturia, dyspnea, pain), lifestyle changes after retirement, poor physical function, and polypharmacy, whereas perpetuating factors may include social isolation, caregiving, and bereavement. 76,78

Nonpharmacologic Therapy of Insomnia

Since the mid-1970s when sleep hygiene education was conceived, nondrug therapy has evolved to target both physiologic and cognitive hyperarousal factors that contribute to insomnia. 79 CBTI, the most effective and comprehensive nondrug approach to treating insomnia, combines cognitive therapy, behavioral interventions, and sleep hygiene education. 10,16 The most recent iteration of CBTI is fully automated digital CBTI (dCBTI) and does not require clinician involvement. dCBTI has the scalability to address insomnia as a public health issue. 5 Other nondrug approaches that may have benefit for some patients include relaxation techniques and mindfulness interventions. 10,16

Sleep Hygiene Education

Teaching patients about behavioral and environmental factors that improve sleep (see Table 3 10,16,80,81 ) can improve sleep over baseline. Practice guidelines recommend against sleep hygiene education (SHE) as a stand-alone intervention because it is less effective than CBTI or mindfulness training 16 ; however, sleep hygiene education is still commonly used in primary care. 79,82 The newest aspect of sleep hygiene education is limiting bedtime screen use, because bright light from devices stimulates wakefulness. 81 Short-wavelength blue light from electronics interferes with natural melatonin secretion. Study results show children and adolescents are particularly sensitive to insomnia worsened by light from electronics, with almost twice the magnitude of melatonin suppression compared with adults. 83

Behavioral Treatment of Insomnia

The goal of behavioral treatment is to break the maladaptive connection between going to sleep and hyperarousal using 2 retraining strategies: (1) sleep restriction and (2) stimulus control. 16 Sleep restriction aims to increase sleep drive by reducing the time spent awake in bed. Time in bed is limited to align with the patient’s sleep duration and requires monitoring of daily sleep and wake times. Stimulus control aims to break the association between being in bed and negative aspects of insomnia, such as wakefulness, frustration, and worry. The underlying rationale is that eliminating these activities allows the bed to be re-associated with sleep rather than arousal. Both strategies may increase daytime sleepiness in the short term. Sleep specialists recommend against sleep restriction in patients with coexisting conditions that sleep deprivation can exacerbate, such as untreated sleep apnea or seizure disorders. 84 Sleep restriction in a person with bipolar disorder may risk triggering mania. 84

Brief Behavioral Treatment for Insomnia

This streamlined 4-session approach, which focuses on stimulus control and sleep restriction, can be delivered by healthcare providers without specialized training. 85 In a clinical trial of older adults, brief behavioral treatment for insomnia was more effective than sleep hygiene education at improving sleep onset latency (SOL), wake time after sleep onset (WASO), sleep efficiency, and sleep quality. 86

Cognitive Treatment of Insomnia

The goal of cognitive therapy for insomnia is to identify and challenge myths and negative beliefs about sleep that perpetuate insomnia, and then replace them with rational thoughts and facts. 16 Cognitive treatment of insomnia includes setting realistic expectations about the amount and quality of sleep any person should expect. 87

Cognitive Behavioral Therapy for Insomnia

Based on robust evidence from many clinical trials, practice guidelines recommend cognitive behavioral therapy for insomnia (CBTI) as first-line treatment of chronic insomnia. 10,16,88,89 The rationale is that CBTI has more durable benefit and fewer adverse effects than drug therapy. In comparative studies, the efficacy of CBTI was comparable with benzodiazepines or benzodiazepine receptor agonists during acute use; however, sedative hypnotics did not have continued benefit after discontinuation. 10 CBTI has demonstrated efficacy for insomnia in patients with coexisting medical conditions, including chronic pain, fibromyalgia, and breast cancer, as well as in perimenopausal women with vasomotor symptoms. 90,91 Efficacy has also been demonstrated for patients with coexisting psychiatric conditions, such as alcohol dependence, PTSD, and MDD. 91

An important CBTI side benefit is improvement in symptoms of coexisting psychiatric conditions, particularly depression. 92 The benefit for depression symptoms appears to be moderated by improvements in sleep quality. Longitudinal data from the Veterans Affairs CBTI program suggest that it reduces suicidal ideation. 93 The proportion of patients endorsing suicidal ideation dropped from 32% at baseline to 21% after CBTI ( P <.001). Each 7-point decrease in ISI score achieved with CBTI was linked to a 65% reduction in the odds of suicidal ideation (OR, 0.35; 95% CI, 0.24-0.52).

Despite guideline recommendations and robust evidence of benefit, few patients receive CBTI. The key access barrier is the lack of trained clinicians. A recent international survey identified 752 CBTI specialists, with almost 90% located in the United States and almost 60% of them concentrated in 12 states. 94

dCBTI products make up the consumer sleep technology (CST) landscape and have the potential to resolve some of the barriers that have prevented widespread uptake of CBTI. Over the last decade, CST (eg, Fitbit) has become ubiquitous. There are more than 10,000 behavioral health apps, most of which focus on relaxation, mindfulness, and meditation. 95 About 10% of adults in the United States may use sleep tracking devices. 87 Analogous to dietary supplements, a software application that makes a wellness claim (eg, better sleep) does not require FDA approval, whereas one that makes a medical claim (eg, treating insomnia) does. The AASM position is that CST must be FDA approved and rigorously tested before adoption into clinical practice. 96 Among the dCBTI products studied most extensively in clinical trials, Sleepio and CBT-i Coach have not sought FDA approval, whereas Somryst (formerly Shuti) is currently being considered for FDA approval. 97-102

How dCBTI compares with in-person CBTI is an important question. In a small randomized controlled trial (n = 90), dCBTI and in-person CBTI had significantly larger treatment effects on the ISI than a waitlist group. 103 However, in-person CBTI outperformed dCBTI on ISI scores and posttreatment depression and anxiety symptoms. In a clinical trial of active military personnel with insomnia, in-person CBTI outperformed online delivery for self-reported sleep quality (d = 0.80), dysfunctional beliefs and attitudes about sleep (d = −0.58), and total sleep time (d = −0.55 to −0.60). 104

Nonprescription dCBTI

As part of a wider initiative to provide digital therapeutics as a health plan benefit, CVS Health is encouraging employers to offer Sleepio as an employee benefit. 105 It is already offered to 10.3 million patients in the United Kingdom’s National Health Service and at least 2 million Americans through their employers. 106 Sleepio has the format of a single-player video game in six 20-minute sessions. In the Digital Insomnia Therapy to Assist Your Life as Well as Your Sleep (DIALS) trial, more than 1700 people with self-reported insomnia were randomized to Sleepio or online SHE. 97 Compared with SHE, Sleepio had a large improvement in sleep-related QOL at week 24 (−18.72; 95% CI, −22.04 to −15.41). Improvements in functional health and psychological well-being were more modest, with respective adjusted differences of 1.76 (95% CI, 1.22-2.30) and 2.95 (95% CI, 2.13-3.76). Almost 20% of participants randomized to dCBTI did not attend the first session, and fewer than 50% completed all sessions. 97

The DIALS trial is one of the few large-scale clinical trials to evaluate potential adverse effects of dCBTI. 97 At week 8 posttreatment, participants randomized to Sleepio or sleep education were asked to rate adverse effects. Patients who received Sleepio had higher rates of fatigue and/or exhaustion (46.3% vs 27.0%; P <.0001); extreme sleepiness (30.8% vs 14.2%; P <.0001); headache or migraine (18.8% vs 12.6%; P = .0084); difficulty with concentration or focus (33.2% vs 19.1%; P <.0001); reduced motivation and/or energy (32.8% vs 24.1%; P = .0032); and irritability (28.2% vs 17.9%; P = .0002) compared with the sleep education group.

Prescription dCBTI

The FDA is considering approval of Somryst (formerly Shuti) as the first prescription dCBTI to treat adults with chronic insomnia and depression. 100 It is also the first product submitted for FDA approval through the Software Pre-certification Pilot Program. Somryst is a software application that provides CBTI and sleep restriction in 6 sessions. 101,102

Clinicians should not assume all dCBTI programs are equal. Programs with a longer duration and more personal clinical support may have greater benefit. 107 Recent data suggest that specific traits of affect and personality influence whether a person responds to dCBTI. 108 These observations highlight how much we need to learn about adherence, predictors of response, drop-out rates, and the clinical infrastructure needed to deliver dCBTI in managed care. 109

Conclusions

Insomnia is a heterogenous and almost ubiquitous disorder with unique predisposing and precipitating factors in vulnerable patient groups. Successful management requires that managed care clinicians understand the factors that drive insomnia in these groups. CBTI effectively treats chronic insomnia in most patients with coexisting medical and psychiatric conditions, in the elderly population, and in those in life transitions, such as menopause. A decade ago, understanding the subtleties of CBTI was a moot point because access barriers, primarily high cost and a lack of trained providers, prevented widespread adoption. Today, managed care clinicians face a vastly different challenge—the relatively unexplored landscape of digital therapeutics. However, dCBTI is here to stay, and it is a scalable option that is being launched in managed care. Now, the issues are which dCBTI product to provide, how to deliver it, how to manage nonresponders and adherence issues, and overall, what role dCBTI will play in the step-care of chronic insomnia. Author affiliation: Julie A. Dopheide, PharmD, BCPP, FASHP, is a professor of clinical pharmacy at the University of Southern California School of Pharmacy and Keck School of Medicine, Los Angeles, CA.

Funding source: This activity is supported by an educational grant from Eisai.

Author disclosure: Dr Dopheide has no relevant financial relationships with commercial interests to disclose.

Authorship information: Substantial contributions to the intellectual content including acquisition of data, analysis and interpretation of data, drafting of the manuscript, and critical revision of the manuscript for intellectual content.

Address correspondence to: [email protected].

Medical writing and editorial support provided by: Jill E. Allen, PharmD, BCPS.

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ORIGINAL RESEARCH article

The different faces of insomnia.

• 1 Department of Internal Medicine and Dermatology, Interdisciplinary Center of Sleep Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany
• 2 Department of Behavioral Therapy and Psychosomatic Medicine, Rehabilitation Center Seehof, Federal German Pension Agency, Seehof, Germany
• 3 Department of Biology, Saratov State University, Saratov, Russia

Objectives: The identification of clinically relevant subtypes of insomnia is important. Including a comprehensive literature review, this study also introduces new phenotypical relevant parameters by describing a specific insomnia cohort.

Methods: Patients visiting the sleep center and indicating self-reported signs of insomnia were examined by a sleep specialist who confirmed an insomnia diagnosis. A 14-item insomnia questionnaire on symptoms, progression, sleep history and treatment, was part of the clinical routine.

Results: A cohort of 456 insomnia patients was described (56% women, mean age 52 ± 16 years). They had suffered from symptoms for about 12 ± 11 years before seeing a sleep specialist. About 40–50% mentioned a trigger (most frequently psychological triggers), a history of being bad sleepers to begin with, a family history of sleep problems, and a negative progression of insomnia. Over one third were not able to fall asleep during the day. SMI (sleep maintenance insomnia) symptoms were most frequent, but only prevalence of EMA (early morning awakening) symptoms significantly increased from 40 to 45% over time. Alternative non-medical treatments were effective in fewer than 10% of cases.

Conclusion: Our specific cohort displayed a long history of suffering and the sleep specialist is usually not the first point of contact. We aimed to describe specific characteristics of insomnia with a simple questionnaire, containing questions (e.g., ability to fall asleep during the day, effects of non-medical therapy methods, symptom stability) not yet commonly asked and of unknown clinical relevance as yet. We suggest adding them to anamnesis to help differentiate the severity of insomnia and initiate further research, leading to a better understanding of the severity of insomnia and individualized therapy. This study is part of a specific Research Topic introduced by Frontiers on the heterogeneity of insomnia and its comorbidity and will hopefully inspire more research in this area.

Introduction

Insomnia is one of the most frequent sleep disorders with continuously increasing prevalence. About 30–50% of the US adult population exhibit insomnia symptoms, 15–20% display a short-term insomnia of <3 months, and 5–15% display a chronic insomnia of >3 months ( 1 – 3 ). Common diagnostic manuals include the ICSD-3 (International Classification of Sleep Disorders, 3 rd Edition, American Academy of Sleep Medicine 2014) and the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5 th Edition, American Psychiatric Association 2013) ( 4 , 5 ). Main characteristics of insomnia include dissatisfaction with sleep quantity and quality with one or more of the following symptoms: difficulties initiating sleep, difficulties maintaining sleep (frequent or prolonged awakenings with problems returning to sleep again), and early morning awakening (occurring earlier than desired after a total sleep time of only 3–5 h with the inability to return to sleep). The disturbed sleep is associated with stress, psychological strain and suffering, as well as impairment in social, occupational, and other important areas of functioning. Complaints include fatigue, exhaustion, lack of energy, daytime sleepiness, cognitive impairment (e.g., attention, concentration, and memory), mood swings (e.g., irritability, dysphoria), impaired occupational functioning and impaired social functioning. The symptoms occur for at least 3 nights per week for at least 3 months and occur despite an adequate sleep environment.

Previous dichotomization of insomnia in primary and secondary (or comorbid) insomnia has been abandoned with the new editions of the DSM-5 and ICSD-3. Currently, insomnia is mostly characterized by the common phenotypes of sleep onset insomnia (SOI insomnia, difficulty falling asleep), sleep maintenance insomnia (SMI insomnia, difficulty staying asleep), early morning awakenings insomnia (EMA insomnia), and a combination of those. Another categorization follows the timeframe of being an acute (<1 month), subacute (1–3 months), and chronic insomnia (>3 months) ( 4 , 5 ). While other sleep disorders (e.g., sleep apnea) are categorized by severity into mild, moderate, or severe, which has important implications for the choice of therapy, insomnia still lacks such a classification. The Insomnia Severity Index (ISI) is the only instrument currently in use that allows for severity classification: no insomnia (score 0–7), subclinical insomnia (score 8–14), or moderate to severe insomnia (score 15–28) ( 6 ).

The characterization of different phenotypes is important to establish clinically relevant subtypes of insomnia. It may help to reduce the heterogeneity of insomnia and facilitate cause identification and personalized treatments. Yet there are not many standardized instruments of insomnia diagnosis allowing for phenotyping. However, there has been evidence that insomniacs with a total sleep time of <6 h suffer a more severe insomnia than insomniacs with a total sleep time of 6 h or more ( 7 ). They display mental and psychological impairment compared to patients with average or longer than average sleep. However, mortality is increased for insomniacs with longer total sleep time ( 8 ). The sleep duration with the 6-h distinction also influences the therapy outcome, success of cognitive-behavioral therapy (CBT), and the relation to comorbid bipolar disorder ( 9 , 10 ). Recently, a study investigated subtypes of insomnia according to psychological stress ( 11 ). Questioning 2,224 volunteers with an ISI score of at least 10 and a control group of 2,098 volunteers with an ISI score below 10, five insomnia subtypes were identified: highly distressed, moderately distressed but sensitive to positive reinforcement (accepting of positive emotions), moderately distressed insensitive to positive reinforcement, slightly distressed with a high reactivity to their environment and life circumstances, and slightly distressed with low reactivity. The results showed a high stability of the classification over the 5-year investigation. The psychological categorization is clinically relevant as there were clear differences identified between the subtypes regarding development, therapy success, presence of electroencephalogram (EEG) biomarker, and the risk for depression. This was a first approach to subtyping insomnia patients according to psychological health. The exact effect of psychological health, family history, comorbidity, personality, environment and sleep quality on insomnia is still unclear. Similar symptom clusters have been discussed for other disorders including depression ( 12 ).

Our study is part of the specific Research Topic introduced by Frontiers on the heterogeneity of insomnia and its comorbidity. We aim to encourage and further the discussion on insomnia heterogeneity and the need for possible phenotyping, we do not intend to provide a complete list of phenotypes or possible clusters. The study picked up the approach of subtyping insomnia by collecting a short questionnaire during anamnesis on possible related symptoms, onset and course of insomnia. We described phenotypical traits of insomniacs with a cohort of sleep disturbed patients from a specialized outpatient clinic for sleep disorders.

Participants and Recruitment

Since 2018, a specialized 14-item insomnia questionnaire has formed part of the clinical routine at the outpatient clinic of the Interdisciplinary Center of Sleep Medicine, Charité—Universitätsmedizin Berlin ( Figure 1 ). The questionnaire is the result of literature research, clinical experience, and consensus of psychologists, neurologist, psychiatrists, and sleep physicians within the sleep center. Patients who visited the outpatient clinic between 01/2019 and 02/2020 and indicated self-reported symptoms presenting a suspicion of insomnia (e.g., difficulties initiating sleep, maintaining sleep, or early morning awakening) according to ICSD-3 criteria were recruited and completed the questionnaire. In total, 486 patients were examined by a physician specializing in sleep disorders and insomnia who confirmed an insomnia diagnosis. The questionnaire did not contain any identifying information. As the questionnaire is part of the clinical routine and the de-identified data has been analyzed retrospectively, ethical review and approval was not required in accordance with the local legislation and institutional requirements. As part of the clinical routine, patients signed informed consent forms allowing de-identified data of their patient file, including the insomnia questionnaire, to be used for research purposes.

Figure 1 . The English translation of the 14-item Insomnia Questionnaire with page 1 and page 2.

Questionnaire

The insomnia questionnaire consisted of 14 items ( Figure 1 presents an English translation of the questionnaire). These included questions related to (1) type of insomnia (SOI—sleep onset insomnia, SMI—sleep maintenance insomnia, EMA—early awakening insomnia, multiple answers possible) at three points in time (start of disorder, progression, current state), (2) progression of insomnia, (3) sleep history of being a light or good sleeper, (4) relatives with sleep disorder, (5) triggers, (6) daytime sleep, (7) sleeping in different environments, (8) sleeping arrangement with partner, (9) alcohol as a sleep aid, (10) referral/ recommendation of general practitioner (multiple answer options), (11) alternative sleep treatments, and (12–14) sleep medication.

Procedure of the examination was standardized and performed by the same physician: On arrival, patients received several sleep questionnaires including the 14-item insomnia questionnaire. They were asked to complete these questionnaires before seeing the physician. During the following in-person consultation, the physician completed a full anamnesis (a patient-reported medical history) and confirmed a diagnosis of a primary insomnia according to ICSD-3 criteria. Next, the questions of the insomnia questionnaire were evaluated. Certain questions were clarified, and missing information added. For example, for question 3, light sleeper was defined. Light sleeper includes patients with a regular bedtime but whose sleep is sensitive to light, temperature, and noise. They need a specific degree of sleep comfort and sleep worse in an unfamiliar environment. These patients can nap during the day and sleep better during vacation and time off (e.g., weekends). They perceive their sleep as non-restorative. They also do not meet the diagnostic criteria of insomnia. The question refers to the time before the insomnia started, mostly referring to childhood / adolescence. For question 6, it was clarified that daytime napping included a daytime situation that explicitly allows for napping. For question 7, it was explained that “weekend” also included the days off work.

Sample size was calculated based on prevalence data and the estimated number of insomnia patients: ca. 30–50% of 328.2 million people (US population estimate 2019) result in about 98.5–164.1 million patients ( 13 ). With an accepted error rate of maximum 5% and a confidence interval of 95%, the sample size was set to at least 400 questionnaires in order to detect sufficiently powerful effects. Statistical analysis was performed using SPSS (IBM SPSS Statistics, Version 20). The patient cohort was described using a descriptive analysis with numbers and percentages ( Table 1 ). In order to investigate possible insomnia subgroups based on phenotypes/characteristics, we compared items with dichotomous answers. Item 7 (sleeping in different environments), item 9 (alcohol as a sleep aid), and item 11 (alternative sleep treatments) each had several subcategories which were consolidated into one overall category. For the text answer of item 5 (trigger) we performed a qualitative data analysis by subjectively grouping the text data and visually presenting the categories. A t-test was used for group comparisons of continuous variables (e.g., age), the chi-square test for dichotomous variables. Significance level was set at 0.05.

Table 1 . Sample description ( n = 456 patients).

Patient Description

Due to missing information that could also not be completed during the in-person consultation with the physician, 30 questionnaires were removed from analysis. The remaining 456 questionnaires were de-identified and analyzed. The patient cohort ( Table 1 ) reported having sleep problems for an average of 11.6 ± 10.9 years (range: 0–82 years, where 0 means the symptoms just started within the past month). The cohort consisted of slightly more female insomniacs (56%) and had an average age of 52.0 ± 15.9 years (range: 18–86 years). More than half of the patients reported having a partner and not living alone (63%), and of those 37% slept in a separate room due to the sleep disorder. If the patient went to a general physician first, 50% were referred to a sleep specialist and 26% to another specialist (neurologist, psychiatrist etc.). In 35% of those cases, the general physician initiated a therapy with sleep medication. In general, 69% of the patients reported having used sleep medication, 23% indicated that they had not. Only 9% mentioned that it was difficult to get sleep medication. While 26% stated they had to pay for sleep medication, 37% said they did not. In Germany, sleep medication for primary insomnia covered by insurance only includes melatonin (only for patients over 55 years) and z-drugs (only for the acute therapy of 4 weeks).

Sleep Characteristics

About 43% of the patients indicated that they had a history of being good sleepers before the insomnia onset, while 48% mentioned that they have always been light sleepers. Forty-three percent reported having a family member with sleep problems. Despite insomnia symptoms, 20% of patients indicated that they were able to fall asleep during the day and 44% sometimes. While 43% of patients reported a trigger for the sleep problems, 42% reported no trigger ( Table 1 ). Figure 2 presents a categorization of the reported triggers. The most frequent triggers were of psychological nature (22%) including depression, anxiety, post-traumatic stress disorder, death of a family member, trauma, rape, psychotherapy etc. Stress was listed as a separate category but is to be considered as a subcategory of psychological triggers (additional 11%). Work related triggers including change or loss of job, freelance work, work problems, shift work, long work hours, workload, mobbing/ bulling etc. accounted for 15%.

Figure 2 . Insomnia triggers organized by categories. Psychological triggers include depression, fear, trauma, etc. Stress may be considered a subgroup of psychological triggers. Family triggers include birth, children, marriage, divorce, etc. Medical triggers include sickness, operations, etc. Work triggers include mobbing, loss of job, change of job, workload, etc. Environment triggers include noise, lighting, neighborhood, etc. Other triggers include smoking, attitude, etc. n/a, not available.

The question about sleep in a different environment (item 7 of the questionnaire) included three subcategories: sleep during vacation, sleep at weekends, and sleep in unfamiliar surroundings. Sleep during vacation was perceived as better by 21% ( n = 84), sometimes better by 30% ( n = 121), and not at all better by 49% ( n = 198). Sleep at the weekend was perceived as better by 18% ( n = 70), sometimes better by 26% ( n = 103), and not at all better by 56% ( n = 224). Sleep in unfamiliar surroundings was perceived as better by 5% ( n = 19), sometimes better by 17% ( n = 68), and not at all better by 78% ( n = 304). We consolidated the subcategories in one general environment variable. First, sleep in a different environment (in general) was considered better if a patient answered “yes (sleep better)” to at least one of the subgroups. The remaining patients were categorized into the sometimes group if they answered “sometimes” to at least one of the subcategories. Then, the remaining patients were categorized into the “no (do not sleep better)” or “no answer” category. In general, 26% indicated that they sleep better in different environments, 28% sometimes, and 37% not at all ( Table 1 ).

The question for alternative non-medical treatments (item 11) also included three subcategories: sport, sleep hygiene, and relaxation techniques. Sport only helped in 7% ( n = 26), helped sometimes in 32% ( n = 130), and did not help in 46% ( n = 185). Sleep hygiene helped in 5% ( n = 18), helped sometimes in 29% ( n = 103), and did not help in 43% ( n = 154). Relaxation techniques helped in 5% ( n = 19), helped sometimes in 32% ( n = 117), and did not help in 38% ( n = 142). We combined the subcategories into one overall variable of non-medical treatment in the same way as for item 7. In general, 9% of the patients indicated that an alternative treatment helps, 42% mentioned it helped sometimes, and 33% reported it did not help at all ( Table 1 ).

Alcohol as a sleep aid (item 9) included two subcategories: alcohol as a sleep aid for sleep onset and alcohol as a sleep aid for sleep maintenance. While 40% ( n = 112) indicated alcohol helps with SOI symptoms, it did not change sleep onset in 41% ( n = 116) and symptoms got worse in 19% ( n = 54). Alcohol helped with SMI symptoms in 11% ( n = 31), did nothing in 46% ( n = 123), and got worse in 43% ( n = 116). We also consolidated this variable. Alcohol as a sleep aid in general helped, if a patient answered “sleep got better” to at least one of the two subcategories (without a “sleep got worse” for the other category). Alcohol worsened sleep if a patient answered at least once “got worse” (without a “got better” for the other category). We added the answer option “alcohol helps sometimes” for patients that answered “got better” to one of the categories and “got worse” to the other. The remaining patients were categorized as “no change” or “no answer.” In general, alcohol helped in 16%, helped sometimes in 11%, and did not help (or even got worse) in 37% ( Table 1 ).

Table 2 presents a further description of insomnia subtypes based on these sleep characteristics. We dichotomized the answers into yes/no in order to create a more equal group distribution for comparison. Patients with a sleep history of being light sleepers even before insomnia onset, had significantly longer insomnia symptoms than patients with a sleep history of being good sleepers ( p < 0.05). Patients with a family history of sleep problems were significantly more frequently female ( p < 0.05), had suffered from insomnia symptoms significantly longer ( p < 0.01), and presented significantly more EMA symptoms ( p < 0.05) than patients without a family history of sleep problems. Patients who were able to sleep during the day were significantly more frequently male ( p = 0.001) and displayed fewer SOI ( p < 0.001) and fewer EMA symptoms ( p < 0.01) than patients who could not sleep during the day. Patients with no trigger displayed a tendency to having a longer insomnia duration than patients with a trigger ( p = 0.05). Patients who were able to sleep better in different environments were significantly younger ( p < 0.001) and showed a tendency to shorter insomnia duration ( p = 0.05) than patients who did not sleep better in another environment. Patients for whom alcohol helped as a sleep aid were significantly younger ( p < 0.001) and presented significantly more SOI symptoms ( p < 0.001).

Table 2 . Description of possible insomnia phenotype subgroups based on sleep characteristics.

Insomnia Symptom Subtypes and Progression

At time of visit, 54% of patients presented SOI symptoms, 66% SMI symptoms, and 45% EMA symptoms ( Table 3 ). In 57% of the patients, there was a combination of those symptoms. Patients with SOI symptoms reported on average that they needed 85.6 ± 55.0 min to fall asleep. Patients with SMI symptoms reported waking up for about 79.0 ± 58.2 min after sleep onset. And patients with EMA symptoms reported that they woke up on average 79.0 ± 56.5 min too early in the morning. Patients with EMA symptoms (not exclusively, combination of symptoms possible) had the shortest history of sleep problems (10.2 ± 9.1 years, range: 0–44 years) compared to patients with SOI symptoms (12.0 ± 9.8 years, range: 0–82 years) and patients with SMI symptoms (11.5 ± 10.6 years, range: 0–82 years). Differences were not significant.

Table 3 . Patient description by insomnia subgroups based on symptoms over time.

Table 3 presents the possible change of sleep symptoms over time by type of sleep symptoms. There was no significant change in SOI or SMI symptoms. Only EMA symptoms significantly increased over time ( p = 0.016). Figure 3 presents the progression in severity of the sleep disorder. Fewer than 10% reported an improvement of symptoms, while in 41% the sleep disorder got worse. In 20% the symptoms showed a periodic pattern. The progression was independent of current symptoms.

Figure 3 . Progression of symptoms by insomnia subgroups. Patients were divided into subgroups of current insomnia symptom. Symptoms are not exclusive, they can occur either as single symptom or in occurrence with other symptoms. SOI, Sleep onset insomnia; SMI, sleep maintenance insomnia; EMA, early morning awakenings insomnia. A patient with a periodic pattern of insomnia experiences weeks or months long periods with insomnia symptoms alternating with symptom free periods. For comparisons between symptom groups, p was calculated with chi-square tests. Results were not significant at a 0.05 level. The sum of the subcategories does not add up to 100% as we refrained from displaying the category “missing data and multiple answers” (7% All patients, 7% SOI, 6% SMI, and 7% EMA).

A distinct cohort of insomnia patients that reported to a special outpatient clinic for sleep disorders revealed that about 40–50% of the patients mentioned a trigger for the sleep problems, were not good sleepers to begin with (light sleepers), had a family history of sleep problems, and had a progressive course of insomnia. Over one third were not able to fall asleep during the day. Insomnia with SMI symptoms was most frequent, as well as a psychological trigger. Over time, EMA symptoms increased. Alternative non-medical treatments were only lastingly effective in fewer than 10%. Over two thirds of the patients (69%) had tried sleep medication. One of the unique traits of our cohort is the duration of the sleep problem before the visit to a specialist (over 11 years). For most, the sleep specialist/clinic is not the first point of contact. Thus, our patient cohort is not comparable to one from a general physician or population-based cohort.

Our results emphasize the insomnia heterogeneity and the need for phenotyping. Following, we will first discuss the characteristics assessed with our questionnaire starting with some new aspects that are currently not commonly asked (history of being a light sleeper, daytime sleep, effects of alternative treatments, alcohol, temporal stability/change of insomnia symptoms). Then, we will review the current literature for further possible phenotypes. Table 4 presents an overview.

Table 4 . Overview of discussed phenotypes.

Phenotypes—Based on Our Cohort

Sleep history.

Almost half of our cohort (48%) presented a bad sleep history, indicative of an idiopathic insomnia.

There are no clear biomarkers or diagnostic criteria to distinguish between psychophysiological and idiopathic (chronic) insomnia ( 14 ). In order to identify idiopathic insomnia, we ask the patient for their sleep history, specifically before insomnia onset. Did the patient always experience poor (light) sleep, or were they a fairly good sleeper? We assume that light sleep is the pre-stage of insomnia, but not every light sleeper needs to develop insomnia, indicating that these variables are not predictors for differentiating between psychophysiological and idiopathic insomnia. Whether this distinction of good and bad sleep before developing insomnia influences therapy will need to be further investigated. Also, the term “light (bad)” sleep needs to be clearly defined and standardized.

Daytime Sleep

Using our questionnaire, we found in our cohort that 34% of patients reported not being able to take a nap during the daytime despite being tired and despite having the explicit opportunity of taking a nap. Those patients were predominantly women with more SOI and more EMA symptoms compared to patients who were able to fall asleep during the day. They did not differ regarding the duration of their insomnia symptoms.

Currently, it is not common during insomnia diagnosis to ask whether a patient is able to fall asleep during the day or to conduct a Multiple Sleep Latency Test (MSLT) for objective assessment. Our own experience with insomnia patients, however, showed how important this question is. We experienced that patients who sleep poorly at night and are tired during the day, but cannot sleep in the day either, usually have a higher degree of insomnia. They tend to suffer for more nights a week and are more resistant to therapy. In contrast, the possibility of falling asleep during the day, in front of the television, in the car, on public transport, in a meeting, or in other quiet surroundings, seems to be a sign of a lower degree of insomnia.

The ability to nap during the day has also been a criterion for other indications in the literature. The Hyperarousal Scale by Regestein et al. ( 37 ) provides indirectly a reference to the degree of alertness during the day and thus to the inability to fall asleep. Khassawneh et al. ( 38 ) used the scale together with the patient's subjective statement that they cannot nap during the day and found that patients with hyperarousal and short sleep duration have more cognitive deficits in memory tests. Li et al. ( 39 ) used the MSLT with a threshold value of 14 min to define hyperarousal. Drake et al. ( 40 ) also used the MSLT and investigated sleep disturbances due to commonly experienced stressful situations to identify factors representing the construct of “stress-related” vulnerability to sleep disturbance. Subjects with a high Ford Insomnia Response to Stress Test (FIRST) score had poorer sleep quality at night and higher latencies of sleep in the MSLT. Roehrs et al. ( 15 ) performed the MSLT in 95 patients with primary insomnia (32–64 years) and in 55 healthy sleepers and found a higher sleep latency in insomniacs (13.2 ± 4.65 min vs. 11.0 ± 4.93 min). However, the difference is small and the variability among insomniacs is high (between 2 and 20 min). The MSLT is still a questionable method for diagnosing insomnia, but it may be a possible tool for subtyping insomnia with regard to the ability to fall asleep during daytime. Espie et al. ( 41 ) examined daytime symptoms of 11,129 participants with ( n = 5,083) and without insomnia, coming from different backgrounds. Of the analyzed items (energy, concentration, relationships, ability to stay awake, mood, and ability to get through work), the items “energy” and “mood” turned out to be the two most important parameters for insomniacs, but not the item “ability to stay awake.” The importance of the criterion daytime sleepiness and/or ability to stay awake seems therefore recognized, but not yet uniformly defined and requires further research.

Alternative Treatment (Behavioral Therapy)

In our cohort, about 83% of the patients have tried at least one of these alternative non-medical behavioral treatments: sport, sleep hygiene, and/or relaxation techniques. In one third of the patients (33%) these techniques did not help. There were no significant age, gender, or symptom differences between patients with effective alternative treatments and patients where it was not effective. However, we did not investigate the severity of insomnia and it may be possible that patients where the alternative treatments did not show a positive effect may be patients with more severe insomnia.

Therapy recommendations for insomnia include a multi-modal behavioral therapy including psychological elements (e.g., CBT) as the first therapeutic step which many patients do complete, most commonly even before they arrange a visit to a specialist ( 42 ). This is also what we found in our cohort. Most of our patients have tried to educate themselves on their sleep problems, have tried to improve their sleep hygiene, have tried alternative non-medical treatments (e.g., sport, relaxation, etc.), and already went to either a natural health practitioner, homeopath, psychologist or psychotherapist. Currently, CBT is not yet good enough established in Germany as a definite treatment for insomnia. Studies have shown that CBT had less of an effect on insomniacs with short sleep duration ( 9 ). We assume that this also applies to patients with a more severe insomnia. However, severity has yet to been clearly defined. Patients will most likely show a similar reaction to phytopharmacology or alternative “smart” therapy (e.g., acoustic or electrical stimulation). A future quality check and standardization of CBT methods may be helpful in order to use the success of alternative treatment/behavioral therapy as a phenotypical criterion. We hypothesize that successful CBT is mainly linked to mild insomnia. For moderate to severe insomnia, CBT should be a necessary concomitant therapy.

In our cohort, only about 26% mentioned that alcohol helps with sleep problems in general. Patients for whom alcohol helped were significantly younger and presented more SOI symptoms. A more detailed analysis showed that alcohol helped especially with sleep onset (40%), less with sleep maintenance (only 11%). In 43% of our patients, alcohol even worsened sleep maintenance, which other studies confirmed ( 16 ). However, in almost half of our patients, alcohol showed no change.

Alcohol is a widely used sleep aid. Asking for the soporific effect of alcohol should become standard during insomnia anamnesis, as well as asking for the soporific effect of drugs (CBD, cannabis, etc.) which have become more and more a topic of sleep research ( 43 ). It is surprising that in our cohort many patients reported a lack of positive effect of alcohol as a sleep aid. It may be that the alcohol amount consumed was not high enough, as we did not ask for specifics.

Symptoms at Time of Insomnia Onset

In our cohort, 57% had SOI symptoms when the insomnia started (in 74% as a combination with other symptoms), 66% had SMI symptoms at the beginning (in 79% as a combination of symptoms), and 40% started with EMA symptoms (in 96% with other symptoms). The majority had a combination of several symptoms. Hence, in most cases of insomnia the sleep disorder started with SMI symptoms (either as single symptom or in combination). We found that patients with single SOI or single EMA were significantly younger than patients with a SOI combination (single: age 47 ± 17 years, combination: age 52 ± 16 years; p < 0.01) or EMA combination (single: age 39 ± 13 years, combination: age 51 ± 15 years; p < 0.01), respectively.

Bjorøy et al. ( 16 ) also investigated subtypes of insomnia in an extensive web-based survey with 64,503 patients who had displayed insomnia for >6 months. Here, 60% of the younger insomniacs (on average 37 years) showed SOI symptoms, either as a combination with SMI and/or EMA symptoms or as a single symptom. Confirming our own results, Bjorøy et al. ( 44 ) also found that SOI as a single symptom was more frequent in younger insomniacs, a SOI symptom combination more frequent in older insomniacs. They revealed further predictors for a symptom combination including female gender, evening chronotype, less education, and being single. While we do not assess aspects such as chronotype, they are important. Literature has shown that there is a higher insomnia prevalence in general in people with an evening chronotype. Insomniacs with a symptom combination also showed a higher comorbidity with depression, anxiety, and a higher use of alcohol and sleeping pills ( 16 ).

Symptom Stability Over Time

Not just the severity, but also the symptoms can change over time. In our cohort, prevalence of SOI and SMI symptoms did not change; EMA symptoms, however, significantly increased from 40 to 45% from first noticing those symptoms to the present (visit to a sleep specialist). Patients with SOI symptoms showed a tendency of an increase of SOI in symptom combination instead of as a single symptom (from 74 to 81%).

An early study of Hohagen et al. ( 17 ) also investigated the progression of insomnia symptoms and possible temporal stability of different patterns in 328 patients (18–65 years). In only 4 months, they discovered a >50% change in SOI, SMI, and EMA symptoms. Only in rare cases did a specific and single symptom insomnia (either SOI, SMI, or EMA) change from one to another single symptom. However, in many single symptom insomnia cases another symptom occurred over time while the first symptom stayed dominant. This tendency was also seen in our cohort regarding the SOI symptoms.

Family History

Almost half of our patient cohort (43%) reported a family history of disturbed sleep/insomnia. These patients were foremost female and presented more EMA symptoms than patients without a family history present.

A specific gene for insomnia is not known but a genetic predisposition cannot be completely ruled out ( 18 , 19 ). A twin study of children revealed a moderate inheritability of insomnia, and another study reported 35% inheritability ( 20 , 21 ).

In our cohort, almost every second patient (43%) reported a trigger. Patients with or without a trigger in our cohort did not differ regarding age, gender, and insomnia symptoms. However, those patients with no triggers showed a tendency to longer insomnia duration then the ones with a trigger. Here, it may be possible that the start of the trigger (whether sudden or slowly, unconsciously developing) may have an impact on the perception of insomnia as a chronic condition. Within our cohort, most frequently named were psychological triggers (e.g., depression, anxiety, trauma, burnout), family triggers (e.g., birth, divorce, custody battles), and medical/biological triggers including surgery and other illnesses. Work triggers (e.g., mobbing/ bulling, job loss) and stress as a separate psychological trigger came next.

Triggers are part of Spielman's theoretical model (1987) of factors causing chronic insomnia. The 3Ps consist of predisposing factors, precipitating factors which trigger acute insomnia, and perpetuating factors ( 22 , 23 ). Triggers would belong to the precipitating factors and may lead to a chronic insomnia. For a working patient, work related stress and job strain may play a bigger role as a trigger and moderator of the insomnia than for those patients that are not working ( 24 ). However, whether the existence of a trigger influences the progression or therapy of insomnia still needs to be further investigated.

Progression of Insomnia

Our patients reported most frequently a negative progression of insomnia (41%); in 26% there were no changes, and only in 7% was there an improvement. On average, the patients suffered from insomnia symptoms for about 11.6 years (range 0–82 years) before seeing a sleep specialist. Patients with predominantly EMA symptoms showed the shortest sleep problem history with 10.2 years (range 0–44 years) compared to patients with SOI or SMI symptoms. About 20% of our patients reported a periodic pattern of symptom severity.

The periodic pattern may be indicative of a non-24 h disorder ( 25 ). A patient with a periodic pattern of insomnia experiences weeks or months long periods with insomnia symptoms alternating with symptom free periods. Green et al. ( 26 ) also investigated the progression of insomnia for over 20 years in 5-year intervals. Patterns included: healthy pattern, episodic pattern, chronic pattern, and a pattern with the development of symptoms in the follow-up period. Chronic insomnia was linked to older women and the working class. It showed that social factors do affect the progression of a sleep disorder, a fact also indicated by Patel et al. ( 27 ) and Arber et al. ( 28 ). There is another distinction of insomnia subtypes by progression introduced by Wu et al. ( 29 ): persistent insomnia, remission, or relapse.

Sleep in Different Environments

Over half of our patients (54%) reported sleeping better in a different environment, including weekends/days with time off from work (51%), vacation (44%), and unfamiliar surroundings in general (22%). The category “unfamiliar surroundings” received the lowest number. Patients may have included job related hotel stays and therefore increased stress level, which may account for the lower number. Patients stating they slept better in a different environment were predominantly younger members of our cohort.

If patients reported sleeping better at weekends or on vacation, this may be an indication that the sleep disorder was caused by work stress or daily routine. In the literature, this is called behavioral induced insufficient sleep ( 30 , 31 ). As only few insomniacs are able to quit their job or family, this category may represent a specific insomnia phenotype. For those, specific interventions are possible including the end of shift work, change to home office work, change from full-time to part-time work, etc.

Further Discussion of Phenotypes

Studies suggest that insomnia is a heterogenic disorder and the identification of different phenotypes or comorbidities is important for personalized treatments ( 45 ). In our study, we presented some new aspects on what insomniacs should be asked during anamnesis and what should be considered during phenotyping. Benjamin et al. ( 32 ) already proposed the following characteristics: (1) life history including demographics, mental and physical health, trauma and life events. This study showed that more women than men and more older people than younger people suffer from insomnia and life events are usually triggers. Such triggers are mostly to be found at home, in health or at work/school, as could also be confirmed with our patients. But who reacts to such a negative trigger with insomnia and why, when, at what age, is not yet known and may possibly have a genetic reason. Further characteristics included (2) subjective sleep quality, (3) fatigue, sleepiness, hyperarousal in the daytime, (4) other sleep disorders, (5) lifetime sleep history, (6) chronotype, (7) depression, anxiety, mood, (8) quality of life, (9) personality, (10) worry, rumination, self-consciousness, sensitivity, (11) dysfunctional beliefs, (12) self-conscious emotion regulation and coping, (13) nocturnal mentation, (14) wake resting state mentation, (15) lifestyle including physical activity and food intake, (16) body temperature, and (17) hedonic evaluation. Other possible non-sleep phenotypes included: MRI, cognition, mood, traits, history of life events, family history, PSG, sleep microstructure, genetics. Blanken et al. ( 11 ) distinguished insomnia subtypes according to the so-called non-sleep categories of life history, mood perception, and personality. Miller et al. ( 33 ) presented an insomnia cluster analysis based on neurocognitive performance, sleep-onset measures of qualitative EEG, and heart rate variability (HRV). They identified two main clusters, depending on duration of sleep (<6 h vs. >6 h). The HRV changes during falling asleep may also play a role, as may the spectral power of the sleep EEG, and parameters from the sleep hypnogram such as sleep onset latency and wake after sleep onset. In one of our own studies, we were able to demonstrate that the increased nocturnal pulse rate and vascular stiffness in insomniacs with low sleep efficiency (<80%) represented an early sign of elevated cardiovascular risk, and thus presented a useful tool for phenotyping insomnia ( 34 ). In the future, other objective characteristics may include biomarkers or radiological features ( 46 , 47 ).

Further characteristics that may play a role but have not yet been mentioned or investigated are the age of the patient during insomnia onset, frequent nocturnal awakenings, the time it takes to see a specialist, and the kind of insomnia onset, slowly progressing or suddenly unexpected. There is no defined age at which the likelihood of insomnia increases, but we know that menopause is a major trigger for women. Grandner et al. ( 35 ) were able to show that getting older alone is not a predictor of insomnia, it rather includes multifactorial events. The question of how long it takes to see a specialist is also part of the Sleep Condition Indicator (SCI) by Espie et al. ( 36 ). They asked whether the insomnia had lasted longer than a year, 1–2, 3–6, or 7–12 months. We can easily agree with such a classification in terms of content. Many patients who wake up frequently at night consider this an insomnia with SMI symptoms. Frequent nocturnal awakenings, but with the ability to fall asleep again straight away, are according to the definition not considered a SMI insomnia. We did not address this in the present study, which presents a limitation. While it is mentioned in the DSM-5 as an independent sign of insomnia, patients affected by frequent nocturnal but subjectively normal sleep lengths and still restful sleep do not (yet) have insomnia. Whether it is an independent phenotype or a preliminary stage of a SMI insomnia should be further examined and defined. It also needs to be clarified whether devices for sleep registration help us with phenotyping. Polysomnography is certainly a very strong phenotypic feature when sleep time is very short, wake times after sleep onset is high and deep and/or dream sleep and sleep efficiency are not optimal. However, the current status is such that it is not suitable for diagnosis ( 48 ). In the near future, technical advances will help to provide objective, long-term sleep data, which are important for diagnosis, subtyping, and therapy for different types of insomnia.

Currently, questionnaires have been used to assess insomnia. The most known questionnaires include the ISI and the Pittsburgh Sleep Quality Index (PSQI). These are valid instruments ( 6 , 49 ). However, there are a number of other questionnaires used for insomnia such as the Amsterdam Resting-State Questionnaire (ARSQ), Dysfunctional Beliefs and Attitudes About Sleep Scale (DBAS), Sleep-Related Behaviors Questionnaire (SRBQ), Sleep Functional Impact Scale (SFIS), Leeds Sleep Evaluation Questionnaire (LSEQ), Glasgow Sleep Effort Scale (GSES) ( 50 – 55 ). In 2014, Espie et al. ( 36 ) introduced the SCI which presented a good instrument for identifying the presence of insomnia and also allowed for time differentiation. Also, the short version with only 2 questions seems valid, where questions are asked about the number of nights in the past month with poor sleep and about the trouble in general caused by sleep ( 56 ). Kalmbach et al. ( 57 ) presented a differentiation between good and bad sleepers based on the Presleep Arousal Scale—Cognitive (PSAS-C) and—Somatic (PSAS-S). People with a high PSAS-C have higher sleep latency and wake times after sleep onset, as well as higher MSLT latency and lower sleep efficiency and total sleep time. The PSAS-C in particular seems to be a good measure of the hyperarousal state. Research and official expert recommendations will show which questionnaires should be favored in clinical practice.

Limitations

Our study intended to encourage and further the discussion on insomnia heterogeneity and the need for possible phenotyping. While we introduced some new aspects of phenotyping, we neither provided a complete list of possible phenotypes nor defined specific clusters. Limitations of our study include the fact that further important aspects (e.g., comorbidity, employment, having children, chronotype, employment etc.) may need consideration. Also, some aspects of the questionnaire will need a more precise definition (e.g., light sleeper, daytime napping, weekend/vacation, alternative treatment, alcohol use), patients were not differentiated regarding sleep duration (<6 h vs. >6 h), and the progression of insomnia was observed retrospectively and not investigated prospectively. While our study was performed with patients of a sleep center, there is also need for phenotyping and thorough assessment of those phenotype characteristics in patients of a primary care setting.

As part of a specific Research Topic introduced by Frontiers on the heterogeneity of insomnia, our study provides further ideas on the already existing approaches to phenotyping insomnia patients. The aim of our study was not to examine all conceivable phenotypic features of insomnia, but to help document specific characteristics with simple questions about the onset and course of insomnia during anamnesis. While the clinical relevance of some of those possible phenotypes is not yet clear (e.g., sleep history, trigger, daytime sleep, sleep in a different environment, alternative treatment, insomnia progression/symptom stability etc.), they should play a role in future research and medical care of insomnia patients. We would like to give an impulse for further research in this area, in order to better differentiate insomnia, thus leading to more effective individualized therapy.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics Statement

Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. The patients/participants provided their written informed consent to participate in this study.

Author Contributions

IF, TP, and VK had the role of supervision and conceptualized the study. IF was responsible for data collection. NL performed data analysis. All authors were involved in visualization and writing including data interpretation, result discussion, and drafting and reviewing the manuscript.

This was not an industry supported study. The study was initiated and funded by the Charité—Universitätsmedizin Berlin owned funding.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank all the patients that participated, and Hendrik Straße and Sandra Zimmermann involved in data entry and processing.

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Keywords: insomnia, phenotypes, subtypes, heterogeneity, symptom, progression, questionnaire, screening

Citation: Fietze I, Laharnar N, Koellner V and Penzel T (2021) The Different Faces of Insomnia. Front. Psychiatry 12:683943. doi: 10.3389/fpsyt.2021.683943

Received: 22 March 2021; Accepted: 24 May 2021; Published: 29 June 2021.

Reviewed by:

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*Correspondence: Naima Laharnar, naima.laharnar@charite.de

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Home — Essay Samples — Nursing & Health — Insomnia — Insomnia: It’s Causes, Symptoms and Effects

Insomnia: It's Causes, Symptoms and Effects

• Categories: Insomnia

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Published: Dec 18, 2018

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Table of contents

Causes of insomnia, chronic insomnia, symptoms of insomnia.

• Insomnia can be caused by unhealthy sleep habits, specific substances, psychiatric and medical conditions, and/or certain biological factors. Recently, researchers have begun to think about insomnia as a problem of your brain being unable to stop being awake because our brain has a sleep cycle and a wake cycle (when one is turned on the other is turned off). Insomnia can be a problem with either part of this cycle; it can be too much wake drive or too little sleep drive. It’s important to first understand what could be causing your sleep difficulties.
• Mental health disorders: Anxiety disorders, such as post-traumatic stress disorder, may disrupt your sleep. Awakening too early can be a sign of depression. Insomnia often occurs with other mental health disorders as well.
• Medications: Many prescription drugs can interfere with sleep, such as certain antidepressants and medications for asthma or blood pressure. Many over-the-counter medications such as some pain medications, allergy and cold medications, and weight-loss products contain caffeine and other stimulants that can disrupt sleep.
• Medical conditions: Conditions linked with insomnia include chronic pain, cancer, diabetes, heart disease, asthma, gastro esophageal reflux disease (GERD), overactive thyroid, Parkinson’s disease and Alzheimer’s disease.
• Sleep-related disorders: Sleep apnea causes you to stop breathing periodically throughout the night, interrupting your sleep. Restless legs syndrome causes unpleasant sensations in your legs and an almost irresistible desire to move them, which may prevent you from falling asleep.
• Caffeine, nicotine and alcohol: Coffee, tea, cola and other caffeinated drinks are stimulants. Drinking them in the late afternoon or evening can keep you from falling asleep at night. Nicotine in tobacco products is another stimulant that can interfere with sleep. Alcohol may help you fall asleep, but it prevents deeper stages of sleep and often causes awakening in the middle of the night.
• Changes in sleep patterns: Sleep often becomes less restful as you age, so noise or other changes in your environment are more likely to wake you. With age, your internal clock often advances, so you get tired earlier in the evening and wake up earlier in the morning. But older people generally still need the same amount of sleep as younger people do.
• Changes in activity: You may be less physically or socially active. A lack of activity can interfere with a good night’s sleep. Also, the less active you are, the more likely you may be to take a daily nap, which can interfere with sleep at night.
• Changes in health: Chronic pain from conditions such as arthritis or back problems as well as depression or anxiety can interfere with sleep. Issues that increase the need to urinate during the night such as prostate or bladder problems can disrupt sleep. Sleep apnea and restless legs syndrome become more common with age.
• Stress: Concerns about work, school, health, finances or family can keep your mind active at night, making it difficult to sleep. Stressful life events or trauma — such as the death or illness of a loved one, divorce, or a job loss — also may lead to insomnia.
• Travel or work schedule. Your circadian rhythms act as an internal clock, guiding such things as your sleep-wake cycle, metabolism and body temperature. Disrupting your body’s circadian rhythms can lead to insomnia. Causes include jet lag from traveling across multiple time zones, working a late or early shift, or frequently changing shifts.
• Poor sleep habits. Poor sleep habits include an irregular bedtime schedule, naps, stimulating activities before bed, an uncomfortable sleep environment, and using your bed for work, eating or watching TV. Computers, TVs, video games, smartphones or other screens just before bed can interfere with your sleep cycle.
• Eating too much late in the evening. Having a light snack before bedtime is OK, but eating too much may cause you to feel physically uncomfortable while lying down. Many people also experience heartburn, a backflow of acid and food from the stomach into the esophagus after eating, which may keep you awake.
• Difficulty falling asleep at night.
• Waking during the night.
• Waking earlier than desired.
• Still feeling tired after a night’s sleep.
• Daytime fatigue or sleepiness.
• Irritability, depression, or anxiety.
• Poor concentration and focus.
• Being uncoordinated, an increase in errors or accidents.
• Tension headaches (feels like a tight band around head).
• Difficulty socializing.
• Gastrointestinal symptoms.
• Worrying about sleeping.

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• Instructions Followed To The Letter
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• Unique And Plagiarism Free

• Insomnia: Causes, Symptoms, and Treatment Words: 797
• Insomnia and Its Negative Health Effects Words: 1151
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• The Problem of Insomnia: Symptoms and Treatment Words: 665
• Insomnia and Sleep Disorders Analysis Words: 698
• Depression: Symptoms, Causes and Treatment Words: 947
• Insomnia and Sleep Disorders Prevention and Management Words: 612
• Scoliosis: Causes, Effects, Prevention and Treatment Words: 1289
• Diabetes: Causes, Treatment, and Magnitude Words: 2345
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• The Effects of Seclusion on Mentally Ill Patients Words: 1755
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• Chronic Patient Education Intervention and Treatment Words: 555

Insomnia: Causes and Treatment

This study aimed to explore to root causes of sleep disturbances, sleeping pills use, and their subsequent side effects among insomniacs. Insomnia is a common health challenge globally with severe health challenges. A thematic analysis was conducted on data obtained from the messageboard posts by seven patients. The findings indicated that there were different causes of insomnia, different methods of interventions and side effects of prescribed sleeping pills. Patients displayed different symptoms, treatment outcomes and adverse effects of drugs. It was concluded that insomnia is a serious medical condition that required individualised intervention or a combination of interventions to avoid certain side effects of self-administered sleeping pills.

Introduction

Sleep disturbances and their related consequences are common among adults and a part of human experiences, as many studies have indicated (Dyas et al., 2010; Moloney, Konrad, & Zimmer, 2011). Insomnia affects many people globally. For instance, over one-third of adults in the UK and North America have reported insomnia (Dyas et al., 2010). Women are more susceptible to sleep disturbances relative to their male counterparts, and the condition increases with age (Morlock, Tan, & Mitchell, 2006). Insomnia has costly consequences such as dysfunction, perturbed diurnal waking state, absenteeism from work, poor quality of life and dependence on sleeping pills.

More than one-third of people with sleep disturbances experience recurring symptoms or chronic conditions. In most cases, insomnia is comorbid and has been associated with physical abuse, depression, anxiety, chronic pain and other physical challenges. Evaluation of patients’ condition is imperative, but effective treatment of the condition leads to better outcomes and improved quality of life.

As studies have shown, most people with insomnia seek medical attention from general practitioners first (Touitou, 2007). Services provided may differ from one GP to another. Patients must confront a new diagnosis, which could be frightening, and doctors often offer sleep hygiene education and prescriptions. Reported cases of insomnia have demonstrated that there is a need to enhance the management of sleep challenges through effective medications, patient education, evidence-based practices noted in psychosocial interventions such as cognitive behavioural therapy.

To offer effective management and enhance patients’ experiences of care for insomnia, it is imperative to understand patients’ beliefs and conditions of the problem and their expectations. In most cases, however, general practitioners have often offered sleeping pills to manage cases of chronic insomnia. Like any other drugs, these drugs have different side effects on different patients. Most users have reported daytime drowsiness and confusion at night. Sleeping pills are powerful hypnotics and could be helpful, but sleep may persist after patients have woken up. Pagel (2005) had observed that previous sleeping pills used to induce sleep were dangerous and addictive, and clinicians failed to address the major causes of the problem. Over the years, however, sleep medications have improved, and understanding sleep problems have increased significantly. It is imperative to take sleeping pills at the right time to avoid daytime side effects. Drugs such as Ambien and Lunesta are common, and patients use them before going to bed. Sleeping pills are effective when taken at the right time, i.e., when one can get a full night of sleep, between seven to eight hours before waking up. A recent study has demonstrated that patients take their sleeping pills in the middle of the night (Roth et al., 2013). These are mainly associated with self-medication tendencies among insomniacs. It is a source of concern as patients become prone to self-administered drugs after nocturnal awakenings, yet little efficacy or safety data exist to support such usages.

This thematic analysis aimed to explore root causes of sleep disturbances, sleeping pills use and other interventions and their subsequent side effects among insomniacs. The study would form part of themes that define causes, pills interventions, and their side effects and outcomes in attempts to manage sleep challenges.

Do clinicians apply integrative approaches or interventions to treat insomnia in patients?

To answer this question, the study had to explore the causes of insomnia, interventions and outcomes of treatments provided.

This topic is important for understanding insomnia, its causes, interventions and outcomes, and therefore, it would contribute to treatment and management.

A qualitative study was conducted using online message board posts for patients with insomnia to explore root causes of sleep disturbances, sleeping pills use, and their subsequent side effects. The researcher was interested in patients’ experiences with different drugs and side effects so that the study could provide majors themes in sleep disturbances management.

A thematic analysis was used to identify major themes in the message board posts. The researcher believed that thematic analysis would provide an accessible and theoretically flexible approach to analyse qualitative data (Braun & Clarke, 2006).

Participants

Participants for the study were chosen from the messageboard posts. They consisted of male and female patients who had suffered insomnia for several years. There were seven participants, consisting of four male and three female chosen randomly from the messageboard. Participants were aged between 26 and 85 years old. These participants were Americans and British. Participants were a good sample because they could offer thematic concerns for sleeping pills use among people with sleeping disturbances. Moreover, they originated from different continents to reflect if treatments and experiences were similar.

Texts for the study were obtained from https://www.everydayhealth.com/ . These posts were made between the year 2010 and 2011. Revolution health was health-based Web site and accessible to global users. Everyday Health provides materials for health education purposes on different health issues to different visitors. It also discusses current health issues to provide personalised health programmes for everyday living (Everyday Health, Inc., 2014).

Data from this Web site were appropriate for the study because of wide coverage and diverse contributions from users or patients.

Procedure and ethics

Data were obtained from the website, as mentioned above. Participants were randomly selected based on their posts, age and gender regarding insomnia. Only relevant texts to the study themes were selected for analysis. Texts were left in their original forms to capture true comments or themes.

Texts were analysed based on themes. Posts were reviewed and coded to identify similar themes. This process was repeated several times to refine and capture three major themes and their sub-themes. Although patients provided different accounts of their experiences, only relevant themes were selected for the study.

Although all study participants provided their names and locations, no names were captured in the analysis. Instead, anonymity was maintained during the coding process by using P1, P2 to P7 for all patients in the study. The material used was readily available from the public domain.

There was no ethical approval for this study because no human subject was directly involved.

This thematic analysis aimed to explore root causes of sleep disturbances, sleeping pills use and their subsequent side effects among insomniacs.

One can simply identify themes as causes, interventions and outcomes or side effects of treatment. Critically, the study showed that there is no single cause of insomnia; sleeping pills alone were common for intervention, but were not effective and had severe side effects. That is, general practitioners did not address the root causes of insomnia.

To answer the research question, the study showed that general practitioners did not use integrative interventions to treat insomnia, but rather prescribed sleeping pills alone, which could not address the root causes of the problem.

Table 1: Table of themes on causes, interventions, and side effects of sleeping pills

Patients with insomnia described different causes of their conditions. For instance, causes of insomnia were related to past physical abuse, lack of care, certain diseases, worrying, anxiety, depression, certain life crisis and tinnitus, among others. These sub-themes showed that causes of insomnia varied among different persons, between male and female and patient of different ages. For instance, P7 wrote that his insomnia resulted from tinnitus .

Patients also used different means to manage insomnia. Majorities sought help from general practitioners, who prescribed sleeping pills. Other patients used different methods, including physical exercise and yoga. It is imperative to note that pills were self-administered, and patients could easily change them, use them at different periods or combine them when they wish. For instance, P6 used a combination of pills and later noted thus, “ I decided to try my experiment – I would take a 30-day supply of Lunesta, followed by a 30-day supply of Ambien, testing to see which was more effective for me ”.

Although some patients reported a lack of side effects with certain pills, majorities reported cases of pain, effects on physical and mental health associated with fatigue, dizziness, anxiety and depression and causes of abnormal behaviours.

Note: ovals show major themes, boxes show sub-themes and arrows show relationships

Three major themes were noted after thematic analysis of the posts on insomnia. Patients mentioned causes, interventions and side effects. Causes of insomnia varied from patient to patient. Still, generally, a history of physical abuse, life crisis, depression, anxiety, use of certain medications and tinnitus were responsible for insomnia among patients who took part in the study. Moloney et al. (2011) noted that ‘medicalization’ was contributing to insomnia in the US. The condition affected patients of both sexes with different ages (Morlock et al., 2006). Severity and effects of insomnia differed among patients.

Generally, many patients consulted their general practitioners when their conditions persisted. Previous studies by Dyas et al. (2010) had shown similar outcomes. Many clinicians did not address the root causes of insomnia. In this study, patients showed that they only received prescribed sleeping pills from general practitioners while there were no attempts to address the root causes of insomnia. Except for the patient who combined medication and exercise and reported positive improvements, others reported continued pain, abnormal behaviours, fatigue and dizziness among other side effects. Other studies have shown that sleeping pills had such side effects, particularly when self-administered (Roth et al., 2013). Patients had tendencies to self-administer sleeping pills, a practice that exposed them to adverse effects of such pills (Roth et al., 2013). It is therefore imperative to use sleeping pills alongside other interventions, such cognitive behavioural therapy to address root causes of insomnia.

Sleeping pills exposed patients to different forms of side effects. However, not all patients experienced similar side effects, while others did not experience such side effects at all with certain pills. This indicates that insomnia resulted from different causes, therefore, required different approaches. No specific interventions were appropriate for all patients. Therefore, clinicians need to understand the side effects of sleeping pills on their patients. Patients must also understand that self-administration of different drugs caused adverse effects on their health.

While this study provided significant insights on thematic issues in insomnia, it had some limitations. Data were gathered from patients’ posts, which did not capture certain data. Moreover, patients did not follow any guideline in their responses and issues of bias were not controlled. A small sample was also used in this study. Nevertheless, the study highlighted failures by patients to adhere to prescription and a lack of patient education on their conditions.

The study implications focus on clinicians and their roles. There is a need to educate patients on the risks of self-administered sleeping pills. Moreover, clinicians should understand the root causes of insomnia before prescribing sleeping pills because pills do not address causes of sleep disturbances.

In conclusion, insomnia is a serious medical condition that requires individualised intervention or a combination of interventions, including cognitive behavioural therapy, to avoid certain side effects from self-administered sleeping pills.

Braun, V., & Clarke, V. (2006). Using thematic analysis in psychology. Qualitative Research in Psychology, 3, 77-101.

Dyas, J., Apekey, T., Tilling, M., Ørner, R., Middleton, H., & Siriwardena, N. (2010). Patients’ and clinicians’ experiences of consultations in primary care for sleep problems and insomnia: a focus group study. British Journal of General Practice, 60(574), e180–e200. Web.

Everyday Health, Inc. (2014). Company Overview. Web.

Moloney, M., Konrad, T., & Zimmer, C. (2011). The Medicalization of Sleeplessness: A Public Health Concern. American Journal of Public Health, 101(8), 1429–1433. Web.

Morlock, R., Tan, M., & Mitchell, D. (2006). Patient characteristics and patterns of drug use for sleep complaints in the United States: analysis of National Ambulatory Medical Survey data, 1997-2002. Clinical Therapeutics, 28(7), 1044-53.

Pagel, J. (2005). Medications and their effects on sleep. Primary Care, 32(2), 491-509.

Roth, T., Berglund, P., Shahly, V., Shillington, A., Stephenson, J., & Kessler, R. (2013). Middle-of-the-Night Hypnotic Use in a Large National Health Plan. Journal of Clinical Sleep Medicine, 9(7), 661-668. Web.

Touitou, Y. (2007). Sleep disorders and hypnotic agents: medical, social and economical impact. Annales Pharmaceutiques Françaises, 65(4), 230-8.

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Insomnia: Introduction

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• N. Darchia 2 &
• I. Gvilia 2  

Nowadays, a high percentage of the population in modern society suffers from various kinds of sleep disturbances, due to the impact of increased physiological and socio-cultural stress factors. One of the most common sleep complaints, which the human being has suffered from since ancient times, is insomnia. Although its literal meaning is a total lack of sleep, in clinical and practical terms insomnia has come to refer to a difficulty in initiating and/or maintaining sleep, or non-restorative, non-refreshing sleep. In a survey conducted in the general population of different countries, the prevalence of insomnia was estimated to be about one third of the adult population. In particular, an epidemiological study conducted in Los Angeles, USA, found that 32% of the population had a current complaint of insomnia [4]. In a study conducted in Mannheim, Germany, the prevalence of insomnia was 31% [12], and in Upper Bavaria - 29% [29]. In Italy, 13% of people rarely or never slept well and 19% reported complaints of insomnia [6]. An epidemiological survey of the French population, based on DSM-IV criteria for the definition of insomnia, demonstrated that 29% reported at least one sleep problem three times per week for a month, whereas only 9% had two or more sleep problems and were classified as “severe insomniacs” [16]. The 1991 National Sleep Foundation Survey [23] in conjunction with the Gallup Organisation conducted telephone interviews with 1000 Americans and found that 36% of them suffered from some type of insomnia; approximately one in four adults reported occasional insomnia whereas 9% claimed that their sleep difficulty occurred on a chronic basis [3]. It should be noted that all these surveys were based on self-reported assessments of insomnia. An epidemiological study based on Polysomnographic recordings is still lacking.

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Darchia, N., Gvilia, I. (2003). Insomnia: Introduction. In: Billiard, M. (eds) Sleep. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-0217-3_14

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Insomnia among College Students - Challenges and Factors

Insomnia is a highly prevalent sleep disorder that regularly affects millions of people worldwide. Dissatisfaction with sleep is further defined as difficulty initiating and/or maintaining sleep or non-restorative sleep, on at least three nights per week for at least 3 months, despite adequate opportunity to sleep. Negative daytime impacts can include significant fatigue, sleepiness, poor concentration, low mood, or impaired ability to perform social, occupational or care giving responsibilities (DSM-5-2013). Insomnia is difficulty falling asleep or staying asleep, even when a person has the chance to do so (NSF-2017). This descriptive study aimed at finding out the prevalence of insomnia among college students and the factors for poor sleep. Using random sampling procedure, 50 Post graduate boys and 50 postgraduate girls who are staying in hostel were selected for the study. Insomnia Severity Index (ISI) with 5 point Likert scale (0=no problem, 4=very severe problem) developed by Charles Morin has been used measuring the sleep disorder. Results revealed that sleep disorders very much prevalent and their lifestyles such as involvement in social networking, stress and peer influence are the predominant factors causing poor sleep disorders. It also has caused poor health and fatigue. This paper emphasized the need for creating awareness on insomnia and its consequences. Constructive Life style education will enhance the wellbeing of students.

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Yugantara Kadam

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One of the human basic need is sleeping. Poor sleep quality due to students' decreased concentration in the classroom would weaken their academic performance.This study aimed to examine the prevalence of various sleep disorders and its relationship with demographic characteristics in dormitory living students in Kermanshah University of Medical Sciences. In this cross-sectional study,)115(females and)85(males students randomly and availability among dormitory students of Kermanshah University of Medical Sciences were selected. In order to collect data, after obtaining students' satisfaction, personal information questionnaire and Pittsburgh standard questionnaire (PSQI) were used. Data were analyzed at a significant level of)p<0.05(using SPSS version 16, and using descriptive statistics techniques (frequency, mean, standard deviation) and inferential statistics (Chi-Square Tests). Findings: In this study,)42.5%(of the subjects were men and)57.5%(were women, age mean was)22 ± 2.3(years.)57.5%(of the students had poor sleep quality which consist)57.3(and)57.6%(of the men and women's population respectively and there did no find significant relationship between sex and sleep quality variable (P = 0.97). There was a significant relationship between sleep quality with consumption of caffeinated beverages (P = 0.01), feeling refreshed in the morning (p = 0.003), difficulty falling asleep (p = 0.001), sense of calm in the morning (p = 0.001), fatigue during the day (p = 0.001). The major consequences of sleep deprivation are drowsiness, dysfunction and grumpy, these factors reduce students' concentration and lead to academic failure. Thus increasing the students' awareness level in terms of sleep hygiene and adverse effects of poor sleep quality can be a useful strategy for improving the quality of students' sleep. Also, authorities can provide suitable educational and welfare conditions for students, take an effective step in enhancing the quality of sleep.

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Bright Light at Russell’s Corners (1946) by George Ault. Courtesy Smithsonian American Art Museum , gift of Mr and Mrs Sidney Lawrence

Spinning the night self

After years of insomnia, i threw off the effort to sleep and embraced the peculiar openness i found in the darkest hours.

by Annabel Abbs   + BIO

I wake up, faintly groggy with sleep, and try to guess the time. Midnight is surprisingly noisy, with a steady stream of traffic bringing people home from the West End in London, while 3am carries a curiously muffled sound, and 4:10am is when the first aeroplane skims my house with its familiar whine of descent. As my ears strain into the darkness, I sense the soft silence of 3am. Once I would have groaned, cursed and plugged the (largely ineffectual) sound of gently lapping waves into my ears. But, tonight, I listen to the emptiness for a few pleasurable moments, then I reach for my notebook and a candle.

I’ve had insomnia for 25 years. Three years ago, after a series of bereavements, I stopped battling my sleeplessness. Instead, I decided to investigate my night brain, to explore the curious effects of darkness on my mind. I’d long felt slightly altered at night, but now I wondered whether darkness and sleeplessness might have gifts to give: instead of berating myself, perhaps I could make use of my subtly changed brain.

I’m not the first person to notice a shift in thoughts and emotions after dark. ‘Why does one feel so different at night?’ asks Katherine Mansfield in her short story ‘At the Bay’ (1921). Mansfield herself became more and more fearful after dark, often barricading herself into her apartment by pushing all the furniture against the front door. And yet, later in life, insomniac nights became one of her most creative times, as she confided to her journal:

It often happens to me now that when I lie down to sleep at night, instead of getting drowsy, I feel more wakeful and I … begin to live over either scenes from real life or imaginary scenes … they are marvellously vivid.

Mansfield referred to her nocturnal imagination as the ‘consolation prize’ for her insomnia.

Around the same time, Virginia Woolf was pondering her own feelings of ‘irresponsibility’ that struck when the lights went down. She too recognised that night rendered us ‘no longer quite ourselves’. After completing each of her books, Woolf was plagued by insomnia – which she made use of to plot out her next novel. ‘I make it up in bed at night,’ she explained of her most inventive novel, Orlando (1928). Night was also a time of epiphany: after protracted struggles with her novel The Years (1937), Woolf’s dramatic breakthrough came ‘owing to the sudden rush of two wakeful nights’ when she was finally able to ‘see the end’. A few years later, the writer Dorothy Richardson noted that, around midnight, ‘she grew steady and cool … it was herself, the nearest most intimate self she had known.’ In her fictionalised autobiography, Pilgrimage (1915-38), Richardson’s alter-ego Miriam finds her most authentic, radical and original self in the solitude of her wakeful nights. For Richardson, reading and writing when she should have been sleeping were acts of resistance, acts that revealed herself to herself, undistracted by the detritus of daylight.

M y night-awakenings began during my first pregnancy. Ten years later – with four children and several years of working across time zones under my belt – a full night of sleep in a single stretch had become a rarity. Most nights, I woke between 2am and 4am, tossed and turned for an hour, then read until I drifted back for a (short) sleep before the alarm went off. I invested in sleep aids: melatonin, weighted blankets, eye masks, sleep-inducing supplements, oils, mattresses, pillows, sheets, pills, apps, bed socks. I experimented with various sleep hygiene routines proposed by ‘experts’. To no avail.

The latest statistics suggest that one in six of us cannot get to sleep, or stay asleep, a figure that is higher for women. At the last count, 8 per cent were taking sleep medication and 11 per cent were regularly splashing out on sleep aids. In 2019, the global market for sleep products was valued at $74.3 billion . Experts predict it will be worth $125 billion by 2031. Frightening, and sometimes misleading, stories appear regularly in the media linking poor sleep to obesity, heart disease, dementia and premature death.

A historical perspective offers us some help here. Sleep deprivation is nothing new: women have always been responsible for night-nursing multiple (often sick or dying) children, elderly relatives and animals; wash days often started at 3am; mattresses were thick with lice; winter nights were ice-cold. Like us, our ancestors suffered from many of the same physiological disruptions now linked to poor sleep, from menstrual and pregnancy cramping to the fluctuating progesterone and oestrogen of the menopause. Like us, they routinely experienced the stresses and anxieties now known to disrupt sleep.

I put away my sleep aids and let my grieving brain lean into the dark nights

Published and unpublished letters and journals show that, for centuries, many women embraced nocturne, finding within it a time of solitude and creativity. The literary critic Greg Johnson in 1990 noted that female writers seemed to have a peculiar talent for making ‘creative profit’ from their insomniac nights. He is right, and not just about writers. Over eight months of wakeful nights, the artist Louise Bourgeois produced her Insomnia Drawings (1994-95), a series of 220 sketches. The Insomnia Drawings were immediately snapped up by the Daros Collection in Switzerland, making instant ‘creative profit’ for Bourgeois, who also credited their production with easing 50 frustrating years of nocturnal tossing and turning. Lee Krasner’s ‘night journey’ paintings, made between 1959 and 1962 in the wake of two bereavements, are now among her most valuable and coveted. Meanwhile, Sylvia Plath wrote Ariel (1965), her most brilliant and acclaimed poetry collection, ‘in the blue dawns, all to myself, secret and quiet.’ Ruth Bader Ginsburg and Margaret Thatcher used the sleeping hours to increase the volume of their (arguably bold) output. Enheduanna watched the stars and produced the poetry that made her literature’s earliest known author . And Vera Rubin discovered dark matter, later saying of these wide-awake and alone nights at the telescope: ‘There was just nothing as interesting in my life as watching the stars every night.’

I call these women my Night Spinners.

Several years ago, when I lost loved ones, my flimsy sleep disintegrated and I lost all appetite for battle. Inspired by aeons of Night Spinners, I put away my sleep aids and let my grieving brain lean into the dark nights. When I woke (which could be any time between midnight and 4am), I got up and wrote, drew, watched the stars. I slept outside (night after night), went for long walks, swam in lunar-light, and taught myself the constellations and the phases of the Moon. I tracked and surveyed glow worms and moths. I watched badgers, and followed the call of owls and nightingales. I discovered a mesmerising nocturnal world.

My nocturnal mind was different. Why did I feel both more fearful and more tranquil? Why was I more inclined to fret and fume? To behave with greater recklessness? Why did images, ideas, memories so often collide in a curious collage of colour and novelty? Writing problems I encountered during the day found solutions as I ambled round the darkened house, peering at the night sky from every passing window. In the middle of sleepless nights, my mind felt less logical, less methodical. My grip on assessing and prioritising less assured. But in return, my inner critic fell silent. Ideas and thoughts meandered, melded and merged. I refused to pass judgment, but in the morning, when I looked afresh at whatever I’d written in the night, I often liked it.

From the work of chronobiologists, we know that our bodies – our blood, breath, bones, saliva and skeletal muscle – change at night. Breast cancer cells divide more quickly. Muscles weaken. Our fat cells, kidneys and intestines become slow and sluggish. Blood pressure drops. Appetites fade. Our temperature falls. Many of these changes appear to be tied not to sleep but to darkness. Scientists are beginning to understand that our brains are also altered at night, most notably as they cycle through a series of sleep stages. As I researched the Night Spinners, a pioneering study called ‘The Mind After Midnight’ (2022) appeared in my email inbox.

A ccording to its authors (a group of eminent sleep scientists in the US), as hormones rise and fall, so the brain shape-shifts. The researchers had noted a greater risk of suicide, self-harm and other ‘risky’ behaviours among depressed people awake at night. They weren’t sure why this happened but suggested a few possible explanations. Was it an evolutionary adaptation designed to keep us vigilant and ready for action at a time when we were once most at risk of predation? Was it a result of synaptic saturation, whereby the brain rests in readiness for another day and so can’t function with its usual deftness and clarity? Was it because of altered hormones – rising melatonin, falling cortisol, dawn-peaking dopamine? Or was it because of the quietening of a vital neural network responsible for executive function, for managing our thoughts, actions and emotions – and known collectively as the prefrontal cortex? The prefrontal cortex (sometimes called our command and control centre, and thought to be the most highly evolved brain region) is very sensitive to sleep and sleep deprivation. Researchers speculate that it takes a restorative break at night – leaving us fractionally less rational, less organised and a little more at the whim of our emotions.

A resting prefrontal cortex might also explain why studies indicate that we are more likely to feel enraged and fearful at night. Or why reformed gamblers, drinkers and smokers are more likely to succumb to old temptations. Or why the celebrated writer Jean Rhys – who frequently wrote at, and about, night – was described by her biographer as ‘a lap-dog’ by day and ‘a wolf’ by night. Rhys liked to rise at a ‘wolfish’ 3am and ‘smoke one cigarette after another’, describing this dark hour as ‘the best part of the day’, when her thoughts were subtly altered. At night, it seems, the filter between us and the outside world is fractionally thinner and frailer. It’s not that our emotions change, but that our ability to control changes. We experience the world more viscerally: the highs are higher and the lows are lower.

The pioneering 15th-century feminist Laura Cereta had subversive ideas as she wrote through the night

This nocturnal rawness and instability could be due to insufficient sleep: when Japanese researchers used MRI to investigate, they found that blood flow between the amygdala (sometimes called the brain’s emotional HQ and our threat-detection hub) and the prefrontal cortex slows down when we don’t get enough sleep. In other words, our night brain could be partly explained by insufficient delivery of oxygen and nutrients to the prefrontal cortex. The researcher Andrew Tubbs – co-author of ‘The Mind After Midnight’ study – thinks that sleep deprivation might act as fuel for the night imagination. Tubbs told me that sleeplessness ‘can increase connectivity between disparate brain regions … as some brain regions become exhausted, [neural] connectivity increases so that other brain parts can compensate.’ He speculates that, as the brain is nudged into processing information ‘in unusual ways, it throws up novel and unusual ideas.’

Studies also suggest that, in women, the prefrontal cortex is larger and more active than in men. Might some women find it easier to free themselves, after dark, from the constraints of their diurnally active brains? Could this explain why Joan Mitchell’s paintings changed dramatically when she began night painting? Or why the pioneering 15th-century feminist Laura Cereta had such subversive ideas as she wrote through the night? Both women certainly thought so – Mitchell continued to paint at night for the rest of her life, while Cereta maintained that her ‘sweet night vigils’ were responsible for the ‘red-hot anger [that] lays bare a heart and mind long muzzled by silence.’

Nightly hormonal change may also affect our insomniac minds, colouring our emotions and perceptions. For instance, scientists now think that dopamine may be both a hormone of creativity and connected to light/dark cycles. When the anthropologist Polly Wiessner studied the Kalahari Bush people, she noticed that the way in which people communicated shifted after dark, becoming more imaginative, evocative and symbolic when gathered around a fire at night. We don’t know whether the speculated evening peaking of dopamine receptors contributed, but Wiessner noticed the way in which this linguistic shift contributed to greater empathy and more tolerance. I too noticed how, awake at night, I often felt more receptive, compassionate and open-minded. Things I might have brushed aside or considered unduly esoteric by day took on a new poignancy and possibility.

A s I embraced sleeplessness, I became aware of the calming effects of scanning the night sky. In 2001, the psychologist William Kelly noticed that many of his students found great pleasure in star-gazing. It seemed to yield a subtly altered state of mind, and Kelly decided to investigate. Over the next decade, he ran a series of experiments, finding that people who enjoyed looking upwards into starry darkness also exhibited greater curiosity, were more open to new experiences, and more inclined to think fantastical thoughts. They were also more likely to wholeheartedly engage with whatever grabbed their interest, to mull over unusual ideas and fantastical possibilities, to seek out novel sensations. Kelly coined the term ‘noctcaelador’, a mash-up of the Latin nocturnus meaning ‘night-time’, caelum meaning ‘sky’, and adorare meaning ‘to adore’.

In 2016, together with his colleague Don Daughtry, Kelly carried out another study . He had an inkling that night sky-watching might also be connected to more lateral thought: his survey of 233 students suggested he was right. Did looking star-wards loosen the imagination, he wondered, or were creative people just more likely to gaze upwards at night? Kelly also wondered whether there might be a third variable influencing the relationship between star-gazing and creativity. Today, awe scientists think that looking at the night sky induces a sense of profound wonder, capable of lowering blood pressure, reducing inflammation, and increasing levels of oxytocin. These scientists might say that Kelly’s ‘third variable’ was a feeling of awe sparked by observing the constellations. But I think Kelly was on to something that goes beyond awe, that he had stumbled on the Night Self – the version of ourselves wired for nocturne.

I needed to retrain my fearful night brain via a steady process of habituation

I discovered another behavioural trait of my Night Self: the psychological effects of an absence of light. We know that women are more affected by darkness. Many of my friends cannot sleep alone in an empty house, let alone take a solitary walk, at night. Studies show that one in two women feels unsafe walking alone after dark, even in a busy public place. Being in darkness frightens many of us. With a less active prefrontal cortex to talk down our fears, wide-eyed nights can balloon into occasions of terror in which we douse ourselves in artificial light, to feel safer.

Fear impedes the workings of our more imaginative and reflective night brain, but several studies have already linked the rise in breast and prostate cancer with excessive night light. Other conditions are being linked to bright nocturnal illumination – depression, anxiety, psychosis, bipolar disorder. Some researchers point the finger at the blue-rich LED lights that have now largely replaced all the earlier incandescent (and less blue-rich) bulbs. I decided that if I was to benefit creatively from my sleepless nights with my health intact, I needed to retrain my fearful night brain via a steady process of habituation. On ever lengthier night walks, I paid close attention to my shifting senses and to my nocturnal amplified sense of sound and smell. Studies suggest that even our olfactory bulb is governed by circadian rhythms, growing more acute after dark.

I grew to love my wakeful nights. All that remained was to rid myself of the fear of an early death – as threatened by endless headlines. The Night Spinners reminded me that premature death wasn’t inevitable: lifelong insomniac Louise Bourgeois lived dementia-free until the age of 98; Proust’s night-working housekeeper, Céleste Albaret, lived until 92; and sleepless star-gazer Caroline Herschel was a healthy 97 when she died in 1848. It helped too that new research trickled out questioning the age-old assumptions. As one longitudinal study stated: ‘In women, mortality was not associated with insomnia and short sleep duration.’ I was not about to die from my broken nights – I was free to enjoy them! Men, however, may need to be a little more circumspect. More research is needed, but early studies indicate that women might be more metabolically resilient to short or broken nights.

To be clear, like any sleep-deprived person, I longed for a luxurious night of uninterrupted slumber. But, as I became acquainted with the gifts of darkness, so my sleep slowly returned. Leaning into my Night Self, being in a darkness that few of us experience in our light-saturated world, provided an antidote to today’s stress-inducing sleep zealotry as well as to my own fear of the dark. I still have runs of splintered sleep, but I no longer let them disturb me. I’ve learnt that a 20-minute power walk reboots my weary brain as well as a nap, that yoga nidra is almost as restful as sleep, and that reflecting when I should be sleeping might be good for my brain. Best of all, I have a fat notebook of night-ish lyrics and poems, the sorts of writings my sensible Day Self would never countenance. One day I might use them for my own ‘creative profit’.

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The top 100 most cited papers in insomnia: A bibliometric analysis

The number of citations to a paper represents the weight of that work in a particular area of interest. Several highly cited papers are listed in the bibliometric analysis. This study aimed to identify and analyze the 100 most cited papers in insomnia research that might appeal to researchers and clinicians.

We reviewed the Web of Science (WOS) Core Collection database to identify articles from 1985 to 24 March 2022. The R bibliometric package was used to further analyze citation counts, authors, year of publication, source journal, geographical origin, subject, article type, and level of evidence. Word co-occurrence in 100 articles was visualized using VOS viewer software.

A total of 44,654 manuscripts were searched on the Web of Science. Between 2001 and 2021, the top 100 influential manuscripts were published, with a total citation frequency of 38,463. The top countries and institutions contributing to the field were the U.S. and Duke University. Morin C.M. was the most productive author, ranking first in citations. Sleep had the highest number of manuscripts published in the top 100 ( n = 31), followed by Sleep Medicine Reviews ( n = 9). The most cited manuscript (Bastien et al., Sleep Medicine, 2001; 3,384 citations) reported clinical validation of the Insomnia Severity Index (ISI) as a brief screening indicator for insomnia and as an outcome indicator for treatment studies. Co-occurrence analyses suggest that psychiatric disorders combined with insomnia and cognitive behavioral therapy remain future research trends.

This study provides a detailed list of the most cited articles on insomnia. The analysis provides researchers and clinicians with a detailed overview of the most cited papers on insomnia over the past two decades. Notably, COVID-19, anxiety, depression, CBT, and sleep microstructure are potential areas of focus for future research.

Introduction

Insomnia has been emerging with more public concerns over the past decades for affecting people’s health and well-being worldwide. The prevalence of insomnia disorder is approximately 10–20%, with approximately 50% having a chronic course ( 1 ). In America, 27.3% of adults reported insomnia 1 year, and the US annual loss of quality-adjusted life-years associated with insomnia (5.6 million) was significantly larger than that associated with any of the other 18 medical conditions assessed, including arthritis (4.94 million), depression (4.02 million), and hypertension (3.63 million) ( 2 ). The economic consequences of the disorder and the cost-effectiveness of insomnia treatments, in aggregate, exceeded $100 billion per year, with the majority being spent on indirect costs such as poorer workplace performance, increased health care utilization, and increased accident risk ( 3 ). Insomnia has been a public health issue and an extensive concern for medical practitioners. The number of insomnia-associated studies has gradually increased annually, of which 27,399 were published accumulatively in Web of Science (WoS) Core Collection from 1985 to 2021.

With a trend of research interest and explosive publication, it is worth identifying the most influential scientific achievements from an abundance of literature on insomnia related topics. So far, there is no perfect method for evaluating the scientific impact that a specific study has had on a scientific discipline, the number of citations of an article is a proxy to indicate the importance of the study ( 4 ). Bibliometric sciences offer both a statistical and quantitative analysis of published articles and provide a measure of their impact in a particular field of research. To date, no such analyses have been performed exploring the most influential works presented in the field of insomnia. In the present study, we aimed to analyze the top 100 most cited articles over the past decades in the field of insomnia with bibliometric citation analysis.

Identification of the top 100 cited articles

The Clarivate Analytics Web of Science Core Collection database was systematically searched on March 31, 2022. The search terms were “insomnia” and “disorders of initiating and maintaining Sleep,” with publication timespan (1985–2022). The publications were ranked by the number of citations, and these were reviewed to identify the top 100 papers with the most citations. Only original articles and reviews with full manuscripts that focused on insomnia as the main topic were included. Literature reviews that briefly summarized published studies were excluded; editorials and consensus statements were excluded. Two reviewers (SL and JJ) independently identified the top 100 papers according to the total citations of the papers, and any disagreement between the 2 reviewers was resolved by consensus involving a third reviewer (XM).

Analysis of the top 100 cited articles

Publications were stratified and systematically assessed according to publication year, country or institute, authors, and journal. Additionally, the frequencies of keywords extracted from the articles were assessed and then included in a network analysis of the development of insomnia.

All data were downloaded from the Web of Science and imported into the bibliometric package (Version 3.0.0) in R software (Version 4.1.3) ( 5 ), which converts and analyses automatically, including the distribution of countries/regions, years of publication, and authors. Publication quality by author was assessed based upon metrics that included the number of publications, citations in the research area, publication h-index value. The h-index is used to quantify an individual’s scientific research output and measure his citation impact ( 6 ).

Networks were constructed using VOS viewer v.1.6.18 ( 7 ) (Centre for Science and Technology Studies, Leiden University, Leiden, The Netherlands), which is commonly used to analyze and visualize relationships among authors, countries, co-citations, keywords, and the terms used in articles.

The Shapiro–Wilk test was applied to test the normality of the distribution of individual variables. We show the mean and standard deviation for data with a regularly distributed distribution and the median and range for data with a skewed distribution. The Tukey method was also employed for plotting the whiskers and outliers. The p -values from pairwise t -tests were adjusted according to either the Bonferroni post-hoc test or Mann–Whitney test to correct for the performance of multiple statistical analyses. All p -values were two-tailed, and a p -value of ≤0.05 was considered to indicate statistical significance. We used a one-way analysis of Kruskal–Wallis test for skewed data. The Mann–Kendall rank correlation was employed to test for correlations among non-parametric variables.

Global trends of annual publication

A total of 44,654 eligible publications were listed in peer-reviewed journals on the ISI Web of Knowledge WoS Core on 31 March 2022. Manuscripts were screened according to inclusion and exclusion criteria and ranked according to citation frequency. The top 100 influential manuscripts were obtained. General information is detailed in Table 1 .

The top 100 most-cited articles in insomnia.

Over the course of 20 years, the total number of citations for the top 100 works of literature varied, but reached a peak in 2021 ( Figure 1 ). The total citation frequency of the top 100 highly cited literature was 58,229 (ranging from 270 to 3,384), with a mean citation frequency of 582.29 and a median citation frequency of 427.5. To exclude the effect of year on citation volume, we analyzed the average annual citation rate of the 100 documents, the highest of which was “Factors Associated With Mental Health Outcomes Among Health Care Workers Exposed to Coronavirus Disease 2019” by Lai et al. ( 8 ) (average annual citation rate of 893.33; Table 1 ).

Global trends in publications on insomnia research.

Most articles on the list were published from 2005 to 2006 ( n = 24), followed by articles published from 2020 ( n = 9; Figure 2A ). The number of citations was high for articles published between 2001 and 2012 (mean total citations = 3762) and decreased for articles published after 2012, but reached a peak in 20 years for articles published in 2020 (citations = 7852; Figure 2B ). The total citation rate of an article was not related to the date of publication ( r = 0.07108, p > 0.05, Mann–Kendall test; Figure 3A ). However, the current citation rate of an article (as measured by the number of citations in 2021) suggests that articles published after 2011 are more likely to have been cited in recent years. This correlation was statistically significant ( r = 0.5394, p < 0.0001, Mann–Kendall test: Figure 3B ).

(A) The total number of publications for each type of article (clinical or review article) according to publication year. (B) The total number of citations publications for each type of article (clinical or review article) according to publication year. (C) Bar graph showing the number of citations (and standard deviation) for the 100 most-cited articles according to type of article (clinical research, review article). Box: lower linee= Box: lower linee number of= Box: lower linee number of citati= median value, white points = outliers. The Tukey method was used for plotting the whiskers and outliers. *Outlier.

(A) Overall citation rate since publication, and (B) current (2021 = last full year) citation rate for the 100 most-cited articles according to the publication date of the article.

Of the 100 articles, 50 were clinical research, 49 were review articles and 1 was basic research. Due to the small sample size of the basic research, we analyzed the number of citations for review articles and clinical research ( Table 2 ) and found that the review articles did not vary significantly with respect to total citations per article compared to the clinical research articles [Mann–Whitney test, p = 0.08; clinical research: median = 397.5 (range = 275–3384); review articles: median = 531(range = 270–2126): Figure 2C ].

Citations for review articles and clinical research.

* P ≤ 0.05.

Distribution of countries and institutes

The global contribution of insomnia research was analyzed and represented by a blue-coded world map in the R software ( Figure 4A ). Of the 35 countries and territories identified for this study, the USA had the highest number of articles ( n = 56), followed by Canada ( n = 22), Germany ( n = 11), Italy ( n = 10) and the UK ( n = 7) ( Figure 4B ). Studies from the USA were the most cited (24,423 citations), followed by Canada (11,832 citations), Germany (6,329 citations), China (5,587 citations) and the UK (3,097 citations) ( Figure 4C ).

Countries contributing to insomnia research. (A) World map showing the distribution of countries in this field. (B) Top 15 countries with the largest number of publications. (C) Total citations of related articles from different countries.

In the co-authorship analysis, a total of eight countries with more than five publications in the field were analyzed ( Figure 5A ). The five countries with the highest total connection intensity were the United States (total link strength = 19 times), Germany (17 times) and Canada (15 times). A total of 235 institutions are involved in this field. Laval University (38 articles) contributed the most publications, followed by Harvard University (11 articles), Stanford University (10 articles), University of Pittsburgh (10 articles), and Duke University (9 articles). We analyzed the co-authorship of 235 institutions with more than five publications. Eight institutional collaborations are shown ( Figure 5B ). The strongest institutions overall were Duke University (total link strength = 14 times).

Co-authorship analysis of countries and institutions. (A) Network map of co-authorship between countries with more than five publications. (B) Network map of co-authorship between institutions with more than five publications. The thickness of the lines indicates the strength of the relationship.

Analysis of author

Considering the number of publications, MORIN CM. is the most productive author, with 17 articles ( Figure 6A ) MORIN CM. was also the top-ranked author in terms of citations in this field (108 citations) ( Figure 6B ).

Analysis of authors. (A) Number of publications from different authors. (B) Total citations in the research filed from different authors. (C) Network map of co-authorship between authors with more than five publications. Size of the circles indicate the number of articles in the 100 most cited list, while the width of the curved line represents the link strength. The distance between two authors indicates approximate relatedness among the nodes.

We analyzed a total of 481 authors, 60 of whom were co-authors in more than two publications. Excluding 36 unrelated items, 24 authors were shown to have collaborated ( Figure 6C ). The author with the highest total linkage intensity was MORIN CM. (total link strength = 40 times).

Analysis of most cited journal

The 100 articles were published in 42 journals. Figure 7 shows the top ten h-index and cited journals that published related articles ( Figures 7A, B ). Of these 42 journals, the highest h-index was Sleep (h-index = 31), followed closely by Sleep Medicine Reviews (h-index = 9). Sleep was cited the most (928 times), followed by Sleep Medicine Reviews (193 times). In the co-citation analysis, we analyzed a total of 1,352 journals, and a total of 52 journals were cited more than 20 times ( Figure 7C ).

Analysis of journals. (A) Total citations in the research filed from different journals. (B) h-index of publications from different journals. (C) Network map of journals that were co-cited in more than 50 publications. The size of the circle represents the number of papers in the top 100 list.

Co-occurrence analysis of keywords

We analyzed a total of 33 keywords that were identified as appearing more than five times ( Figure 8A ). The colors in the overlay visualization shown in Figure 8B indicate the average year of publication of the identified keywords. The keywords which published after 2011 are colored more green or yellow. The density visualization shows the same identified keywords mapped by frequency of occurrence ( Figure 8C ).

Co-occurrence analysis of keywords. (A) Mapping of keywords of studies. (B) Distribution of keywords according to average publication year (blue: earlier, yellow: later). (C) Distribution of keywords according to the mean frequency of appearance. Keywords in yellow occurred with the highest frequency.

Citation and co-citation analyses

The citation analysis showed 94 pieces of literature with more than 50 citations ( Figure 9A ). As shown in Table 1 , “Validation of the Insomnia Severity Index as an outcome measure for insomnia research” [Bastien et al. ( 8 )] was cited 3,384 times, followed by “Factors Associated With Mental Health Outcomes Among Health Care Workers Exposed to Coronavirus Disease 2019” [Lai et al. ( 8 )] with 2,680 citations and the third most cited is “Epidemiology of insomnia: what we know and what we still need to learn” [Ohayon ( 10 )], with 2,126 citations.

(A) Network map of citation analysis of documents with more than 50 citations. (B) Network map of co-citation analysis of references with more than 10 citations. The size of the circle represents the number of papers in the top 100 list.

We analyzed 38 references that were co-cited more than 10 times in total ( Figure 9B ). The three most cited references were Ford de. ( 107 ) (1989, JAMA-J AM MED ASSOC; 33 citations), Ohayon ( 10 ) mm. (2002, sleep med rev; 30 citations), and Breslau ( 108 ) (1996, bio psychiat; 29 citations).

General trends in insomnia research

Bibliometrics allows for quantitative analysis of a researcher’s individual achievements, or even a country’s or institution’s contribution and international impact in the field, through a statistical analysis of the total number of academic papers published in a clinical field and the total frequency of citations ( 109 ). In this study, we combined bibliometric analysis with network visualization to identify the initial 100 most influential manuscripts in the field of insomnia based on global citation frequency, highlighting the contributions that have led to significant advances in insomnia research and pointing to current trends in the field.

With the largest number of publications and citations, and the highest co-authorship analysis ranking by country, the United States is currently the world leader in insomnia research. These results suggest that the US is likely to have a major impact on the direction of research in the field and has the strongest collaboration globally. The citations of articles from Canada, Germany, Italy and the UK have also increased significantly over the last three decades. China has a small total number of publications, but ranks fourth in total citations; it ranks sixth in collaborations with other countries, indicating that China has an influential publication in the field of insomnia and actively maintains close collaborations with other countries. The Laval University Institute is the most productive, with 38% of the publications, while Duke University ranks first in the co-authorship analysis, indicating its close cooperation with other institutes.

Influential authors and studies in insomnia

Morin, C.M. has the largest number of publications and citations and also ranks first in co-authorship analysis conducted by authors. Of these top 100 highly cited publications, Morin C.M. has published 17 articles, 8 of which he is the first author. Dr. Morin is interested in the validation of assessment scale for insomnia. Utilizing scales to evaluate the therapeutic effects of insomnia is the most convenient and widely used method, and the reliability and validity analysis results are critical for the scale to be used as an outcome indicator. Dr. Morin examined psychometric indices of the Insomnia Severity Index to evaluate treatment response in a clinical sample ( 9 ), and validated the Dysfunctional beliefs and attitudes about sleep, providing a variety of indicators for the assessment of insomnia ( 10 ). Nevertheless, the original version of the ISI and the PSQI are the most commonly used, and the original version of the ISI remains the only validated scale that is highly recommended for all insomnia research protocols. Dr. Morin has also conducted extensive research on cognitive behavioral therapy for insomnia and its comorbidities ( 110 , 111 ). His team’s current efforts continue to focus on evaluating the efficacy of cognitive behavioral therapy and optimizing the procedural approach ( 112 , 113 ).

According to the literature citation analysis and reference co-citation analysis, the most frequently cited Bastien et al. ( 8 ) reported clinical validation of the Insomnia Severity Index Scale (ISI) as a brief screening indicator for insomnia and an outcome indicator for treatment studies, indicating that the ISI is a reliable and valid tool for quantifying perceived insomnia severity. The ISI is a brief self-report instrument designed to assess subjective symptoms and daytime status of insomnia and the extent to which insomnia causes worry or distress. The ISI has been continually validated and the study by Bastien et al. was the first formal psychometric analysis of the reliability and validity of the ISI. Further validation of the ISI using item response theory (IRT) analysis was reported by Morin et al. ( 114 ), obtaining evidence on internal consistency, item response patterns and convergent validity, yielding new evidence on optimal sensitivity and specificity indices for case finding and assessment of minimal important changes following treatment ( 12 ). A recent meta-analysis ( 115 ) reported on the construct validity of the Insomnia Severity Index (ISI), which showed that studies reporting validated factor analyses (CFA) had more reliable results than those reporting only exploratory factor analyses (EFA), and that two-factor solution were strong expressions of dimensionality and higher reliability indicators for the ISI compared to three-factor solutions.

Future outlook

Our co-occurrence network diagram, categorized by subject area or date of publication, shows current hotspots and future directions in insomnia research ( Figures 8A–C ). The keywords indicate that insomnia research involves a wide range of populations (elderly, adolescents), causal factors (quality of life, coronavirus), disorders (anxiety disorders, depression) and therapies (cognitive behavioral therapy, pharmacotherapy). The most recent keywords indicating future trends in the field are as follows:

COVID-19 and insomnia

The total number of citations in the insomnia-related literature rose significantly in 2021, reaching a peak in the last 20 years. This may be related to the outbreak of the Corona Virus Disease 2019 (COVID-19). The impact of the new coronavirus pneumonia outbreak has led to an increase in psychological disorders in the population and a climb in the prevalence of insomnia, with 36.7% of adults from 13 countries having clinical symptoms of insomnia and 17.4% meeting diagnostic criteria for insomnia ( 24 , 114 ). Spielman identified negative life events and other stressors as triggers for the development of insomnia ( 116 ), with up to 37% of the population experiencing insomnia in the presence of stressful events ( 117 ). During the early stage of the COVID-19 pandemic, insomnia symptoms were mainly associated with acute psychological reactions due to the rapid spread of the disease and strict enforcement of restrictions, as well as poor sleep hygiene ( 118 ). During the late stage, insomnia symptoms are associated with economic stress associated with the COVID-19 pandemic ( 118 ) and the impairment of sleep patterns ( 119 ). Recent studies have shown that into the late stages, sleep is characterized by significant objective sleep fragmentation in the presence of adequate sleep duration ( 120 ), suggesting that the adverse effects of the initial pandemic outbreak on sleep will persist. Studies of insomnia during the COVID-19 pandemic highlight the importance of focusing not only on the primary diseases, but also on the psycho-psychological issues, particularly insomnia during global public health events.

Depression, anxiety, and insomnia

In our analysis of keywords, we found that “anxiety,” “depression,” and “mental disorders” were frequently mentioned in 100 documents as the second most frequently occurring keywords after “insomnia.” Studies have shown that there is a strong relationship between insomnia, depression and anxiety, with insomnia considered a risk factor for anxiety and depression ( 121 ), with those suffering from insomnia 9.82 times more likely to have clinically significant depression and 17.35 times more likely to have clinically significant anxiety compared to those without insomnia ( 38 ). Anxiety and depression are also considered risk factors for insomnia ( 122 ), suggesting that insomnia is bilaterally associated with psychiatric disorders such as anxiety and depression ( 41 ). In terms of biological mechanisms, polymorphisms and dysregulation of the serotonin, dopamine(DA), oxytocin (OXT) and genes may be associated with the development and maintenance of insomnia and mood disorders ( 123 ), while behavior and thoughts can in turn affect the activity of the serotonin, DA, OXT, and genes ( 124 ). In terms of brain function, sleep disturbances have been shown to disrupt the function of cortical neural circuits, including the amygdala, striatum, anterior cingulate cortex and prefrontal cortex (PFC) ( 125 ), which play a key role in the regulation of the affective system ( 126 ). In addition, there is growing evidence that insomnia disrupts brain functions associated with the reward system ( 127 , 128 ), and that dysfunction of the reward system is associated with a variety of neuropsychiatric disorders ( 129 ), including depression, bipolar disorder ( 127 , 128 , 130 ) and others.

Subtypes of insomnia

Insomnia is a heterogeneous disorder ( 131 ), and identifying clinically relevant subtypes of insomnia disorders can help reduce heterogeneity, identify etiology, and personalize treatment ( 132 ). In Ohayon ( 10 ) proposed that epidemiological studies should focus on distinguishing different subtypes of insomnia. Typing by sleep stage symptoms, such as difficulty falling asleep (DIS), difficulty maintaining sleep (DMS), early awakening (EMA), or a combination of four subtypes ( 133 ); typing by insomnia episodes and duration, such as chronic insomnia, short-term insomnia ( 134 ); and typing by primary and secondary clinical features of insomnia, such as primary insomnia, secondary insomnia ( 135 ). Although these subtypes can differ in terms of stable sleep-related characteristics, reliability and validity are lacking and heterogeneity still prevails ( 136 ). It remains difficult to find consistent insomnia features in terms of cognition, mood, personality, life history, polysomnography, and sleep microstructure, and this inconsistency suggests that different subtypes of insomnia disorder have not been fully identified ( 137 ). For a long time, researchers have been working on different aspects of the subtypes of insomnia disorders, such as natural history of insomnia ( 94 ), subjective and objective sleep duration ( 74 ), sleep microstructure ( 138 ), non-insomnia characteristics (life history, affective and personality traits) ( 137 ), and clustering subtypes of insomnia (subtyping based on subjective sleep variables as well as age at onset of insomnia, the severity of anxiety and depressive symptoms) ( 139 ). Vgontzas et al. ( 74 ) proposed that insomnia with short objective sleep duration is the most biologically severe phenotype of the disorder and is associated with a higher risk for hypertension, diabetes, and other diseases. Also, it appears that insomnia with objective short sleep duration is a biological marker of genetic predisposition to chronic insomnia. In the future, the underlying genetic, neurobiological, and neuropsychological mechanisms of insomnia with objective short sleep duration could be further explored. In terms of polysomnography ( 140 ), brain imaging ( 141 ), and genetics ( 142 ), we can also examine the association of other sleep variables with other phenotypes of insomnia.

Cognitive behavioral therapy

Cognitive behavioral therapy (CBT) is the most widely researched form of psychotherapy, which leads to changes in emotional distress and problem behavior by altering therapeutic strategies that are maladaptive to poor cognition ( 14 ). CBT for insomnia (CBT-I) has long been shown to be more effective than control therapy ( 143 ). Cognitive behavioral therapy for insomnia (CBT-I) is now commonly recommended as a first-line treatment for chronic insomnia because of the potential for sustained benefit from psychotherapy without the risk of tolerance or adverse effects associated with pharmacological approaches ( 65 ). Recent evidence suggests that CBTI can also be used to treat acute insomnia caused by stress ( 144 ). Many elements of this treatment approach can be applied to stressful events such as the current COVID-19 pandemic and can be adapted to treat and prevent sleep problems resulting from confinement, increased stress and changes in circadian and daily activities ( 78 ). The development of technologies such as the Internet, big data and artificial intelligence has brought about a boom in digital medicine in the healthcare industry, enabling the digitization of CBT-I ( 145 ), and the effectiveness of digital cognitive behavioral therapy (dBT-I) for insomnia has been validated ( 146 ). In recent years, dBT-I has been widely used during the COVID-19 pandemic, and Liu et al’s ( 147 ) study provides an entry point for building a dBTI platform and a theoretical basis for clinical application.

Sleep microstructure

In recent years, sleep microstructure has gradually gained widespread attention, and a number of the 100 articles we examined have begun to focus on slow-wave sleep. Slow wave sleep (SWS) is a component of non-REM sleep that is important in neurophysiological processes like memory and cognition ( 148 ). According to the “active system consolidation hypothesis,” slow oscillations, in conjunction with sleep spindle waves, drive the repetitive reactivation of newly encoded memories during slow-wave sleep, facilitating their integration into long-term memory storage sites ( 149 ). A growing body of research confirms that auditory stimulation ( 150 ), transcranial direct current stimulation ( 151 ), and medication ( 152 ) are all effective in improving memory function by enhancing slow waves of sleep ( 153 ). Slow-wave sleep is not only used for memory enhancement, but has also been widely used to improve cognitive function in patients with mental illness ( 154 , 155 ) and for sensory-motor recovery in stroke patients ( 156 ). Recent studies have shown that enhancing SWS in healthy individuals profoundly affects the connections between the endocrine and autonomic nervous systems ( 157 ), opening up a wide range of potential applications for enhancing SWS.

Strengths and limitations

To the best of our knowledge, this is the first bibliometric analysis of the Insomnia research trend. Using the R bibliometric package, we conducted a comprehensive survey of the literature to perform quantitative and qualitative analyses of the publication output and quality of studies from various authors. We also used a well-known scientometric software tool (VOSviewer) to build and visualize the bibliometric networks by analyzing co-authorship, co-citation, and co-occurrence. Nevertheless, our analyses have some limitations. Firstly, the search is primarily conducted in the WoS database. Although WoS is the most commonly used database in scientometrics, it is advisable to combine the results with those from other databases, such as PubMed and Scopus. Secondly, our search did not separate mechanistic studies from clinical studies, ignoring the research progress in mechanistic studies; however, this could also indicate that mechanistic studies in the field of sleep could be strengthened. Third, the keyword analysis results may have been influenced by incomplete keyword extraction. To better display the keywords, keywords that appeared more than five times in the network were shown. Fourthly, as this is a developing area of research, we may have overlooked the contribution of analyzing recently published studies because of their low citation frequency, despite some studies being published in high quality journals.

In conclusion, to our knowledge, this is the first bibliometric study to identify the 100 most cited papers in insomnia research. Our results suggest that the outbreak of the COVID-19 epidemic is strongly associated with the onset of insomnia and stimulates the researcher’s interest. The key words suggest “COVID-19;” “anxiety,” “depression,” “CBT,” and “sleep microstructure” are currently hot topics in the field of insomnia and will be future research trends in the field, indicating that the focus of research has shifted from insomnia epidemiology and scale validation to the study of co-morbidities and sleep microstructure of insomnia. Despite its limitations, citation analysis provides an important quantitative approach to research in the field of comparative science. The findings of this study may provide a valuable reference for researchers to guide and implement their scientific research interests in the field of insomnia.

Author contributions

QW, KL, and WW designed the study. QW and KL wrote and revised the draft manuscript and carried out data visualization and graphical interpretation. QW, KL, SL, JJ, and XW performed the literature search, retrieval, and data collection. WW provided the critical assistance or funding. All authors contributed and approved the final draft of the manuscript before submission.

Acknowledgments

We acknowledge the support of the Team of the Insomnia Research Team of Jiangsu Province Hospital of Chinese Medicine, Affiliated Hospital of Nanjing University of Chinese Medicine.

This work was supported by the National Natural Science Foundation of China (grant number: 82274631) and Jiangsu Provincial Department of Science and Technology (grant number: BE2021751).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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