Risk factors, comorbidities, and consequences of insomnia in adults

INTRODUCTION — 

Patients with insomnia have difficulty initiating sleep, difficulty maintaining sleep, and/or waking up early in the morning without the ability to return to sleep. For a diagnosis of insomnia disorder, the symptoms occur at least three nights per week for three months, and patients also must report significant daytime symptoms such as fatigue, sleepiness, inattention, mood disturbance, or impaired performance [1].

Insomnia is one of the most common symptoms encountered in medical practice. In addition to immediate consequences reported by patients, insomnia also precedes or accompanies medical or psychiatric disorders and may occur as a response to physiologic or psychological stressors.

This topic provides a general overview of the epidemiology, risk factors, comorbidities, and consequences of insomnia. The evaluation, diagnosis and management of insomnia are discussed separately. (See "Evaluation and diagnosis of insomnia in adults" and "Overview of the treatment of insomnia in adults" and "Cognitive behavioral therapy for insomnia in adults" and "Pharmacotherapy for insomnia in adults".)

EPIDEMIOLOGY — 

Insomnia is a common medical complaint that generates over five million office visits per year in the United States alone [2].

Prevalence estimates vary according to the study design and definition of insomnia used. In cross-sectional surveys of ambulatory patients, one-third to two-thirds of adults report insomnia symptoms of any severity, and approximately 10 to 15 percent have chronic insomnia with daytime consequences [3-7]. Approximately one-third of adults have one or more symptoms of trouble falling asleep, trouble staying asleep, and/or nonrestorative sleep [8].

Insomnia is more common in older adults, with a pooled prevalence of 20 percent for insomnia disorder [9]. Women are 1.2 to 1.4 times more likely to have insomnia, starting during puberty and worsening during pregnancy and peri- and postmenopause [10-12]. Across all groups, prevalence is increased in association with a wide range of stressors including unemployment, divorce, widowhood, low socioeconomic status, and self-reported discrimination [13-16]. Rates are also higher in those with psychiatric or substance use disorders [11].

PATHOPHYSIOLOGY — 

Chronic insomnia is associated with physiological activation, even in the absence of a comorbid medical or psychiatric condition. Compared with good sleepers, individuals with insomnia have alterations in presleep cognitive activity, with both qualitative and quantitative differences that include more planning, problem solving, and unpleasant thoughts and worries [17]. A majority of studies have found increases in physiological activation, including cardiac, metabolic, hormone, and high frequency electroencephalographic (EEG) measures [18,19].

A systematic review of imaging studies concluded that the anterior cingulate cortex, thalamus, insula, precuneus, posterior cingulate cortex, and middle frontal gyrus have been most frequently identified as showing structural, functional, or metabolic differences in insomnia subjects, generally consistent with the hyperarousal theory [20].

RISK FACTORS AND COMORBIDITIES — 

Insomnia has a complex relationship with other medical and psychiatric disorders and is no longer considered "primary" or "secondary" depending on the presence or absence of an associated condition. In practice, the vast majority of patients have one or more risk factors or comorbidities that may be contributing to insomnia, and successful treatment requires attention to the insomnia itself as well as relevant comorbidities (table 1).

Intrinsic factors and genetics — Insomnia may be more common among people with a physiological or psychological vulnerability. Individual factors associated with an increased risk of insomnia include [8,21,22]:

●Older age

●Female sex (especially peri- and postmenopausal)

●Previous episode of insomnia

●Family history of insomnia

●Predisposition toward being more easily aroused from sleep

●Trait sleep reactivity (ie, the propensity for exaggerated sleep disruption in response to stressful events)

●Psychiatric and psychological factors (eg, anxiety, depression, increased daytime stress reactivity)

A genetic basis for insomnia is not well characterized and is likely complex. Insomnia often runs in families, and studies have identified genetic and epigenetic factors that are associated with insomnia [19,23]. Genome-wide association studies suggest that insomnia is a highly polygenic trait, with insomnia-associated risk loci overlapping with loci associated with risk profiles for depression, anxiety, neuroticism, type 2 diabetes, coronary artery disease, and low subjective well-being [24-26]. Epigenetic mechanisms related to stress exposure during development also appear to impact both sleep and stress reactivity, thus increasing risk for insomnia.

Psychiatric disorders — Chronic insomnia and psychiatric disorders frequently coexist [27], and individuals with psychiatric illnesses show objective evidence of disturbed sleep, including decrements in total sleep time and sleep efficiency and prolonged sleep latency [28]. Approximately one-half of patients with chronic insomnia have a psychiatric disorder, and the majority of those with a psychiatric disorder have insomnia [3,29].

It can be challenging to identify psychiatric comorbidities in patients with insomnia, as patients may deny or minimize the role of the psychiatric disorder. As an example, a patient might say, "I would not be depressed if I could get a good night of sleep." Clinicians, on the other hand, may have a tendency to assume that insomnia is caused by the psychiatric disorder and focus more on the psychiatric condition, with the expectation that the insomnia will improve as the psychiatric condition improves. This may be a false assumption, as insomnia often persists independently.

Insomnia frequently precedes the development of psychiatric illness [30-32]. In prospective studies, individuals with self-reported insomnia are at significantly increased risk of developing a new psychiatric disorder (particularly major depression, but also anxiety disorders, psychosis, and alcohol use disorder) within one year or longer compared with individuals without insomnia.

Depression — Insomnia (or hypersomnia), when it exists along with depressed mood or loss of interest or pleasure, is one of nine diagnostic symptoms of unipolar major depression. Around 40 percent of people with insomnia have clinical depression, and up to 80 percent of patients with depression report insomnia symptoms, which frequently predate the development of depression [30,31,33]. (See "Approach to the adult patient with suspected depression".)

Early morning awakening is a hallmark symptom of depression, but adolescents and young adults with depression may primarily report difficulty initiating sleep. Depressed patients may also complain that they have not slept at all for one or more nights, although sleep recordings of these nights show reduced (not absent) sleep. Depression is variably associated with a reduced latency to rapid eye movement (REM) sleep, including increased REM sleep in the first one-third of the night, and increased volume and intensity of REM sleep [28,34]. (See "Stages and architecture of normal sleep".)

Treatment effects are also bidirectional but may be incomplete, and directed treatment of each disorder may be required. In a meta-analysis of 23 trials of nonpharmacologic or pharmacologic treatment for insomnia in patients with comorbid depression, insomnia therapy led to moderate to large improvements in depression outcomes as measured by the Hamilton or Beck depression scales [35]. Another meta-analysis of 49 studies demonstrated that nonpharmacologic treatment of insomnia also reduced depressive symptoms in individuals with and without depression [36]. Simultaneous treatment of both disorders can increase the likelihood of an insomnia response and lead to more rapid control of depression at lower doses of antidepressant medication [37]. (See "Overview of the treatment of insomnia in adults", section on 'Patients with comorbid psychiatric disorders'.)

Anxiety — Like depression, anxiety disorders share diagnostic overlap with insomnia. The majority of patients with anxiety report insomnia [38]. Overall, anxiety disorders including generalized anxiety and posttraumatic stress are associated with increased subjective sleep disturbance, decreased total sleep time, and decreased sleep continuity [39]. A meta-analysis of longitudinal studies found that insomnia is highly predictive of development of anxiety disorders, similar to its relationship with depression [40]. Treatment of both anxiety and sleep symptoms with pharmacotherapy or cognitive behavioral therapy for insomnia (CBT-I) improves outcomes [41,42]. (See "Generalized anxiety disorder in adults: Epidemiology, pathogenesis, clinical manifestations, course, assessment, and diagnosis" and "Panic disorder in adults: Treatment overview".)

Substance use disorders — Insomnia is very common among patients with substance use disorders across a variety of substances and stages of illness. It predates alcohol dependency in the majority of patients with alcohol use disorder and is an important risk factor for relapse to drinking among those who have achieved abstinence [31,43-46]. Treatment of insomnia with CBT-I improves sleep and reduces measures of alcohol dependency [42]. (See "Insomnia in patients with a substance use disorder".)

Posttraumatic stress disorder — Patients with posttraumatic stress disorder (PTSD) frequently have insomnia. Specifically, a meta-analysis estimated a 63 percent prevalence of insomnia in those with PTSD [47], and insomnia prior to trauma increases risk for developing PTSD [48]. Insomnia in PTSD is frequently associated with nightmares and fear of falling asleep or returning to sleep [46,49-51]. (See "Posttraumatic stress disorder in adults: Epidemiology, pathophysiology, clinical features, assessment, and diagnosis" and "Nightmares and nightmare disorder in adults".)

Medical conditions — Insomnia that follows a chronic course can be comorbid with a medical illness and/or related to the medications required to treat the medical illness (table 1). A systematic review found that the presence of insomnia or symptoms of insomnia were associated with a greater prevalence and/or number of chronic diseases [52]. Conversely, approximately 40 percent of patients with a medical problem have insomnia that follows a chronic course, compared with 8 percent in a control population [53].

Medical conditions that are often associated with chronic insomnia include pulmonary disease, hypertension, diabetes, cancer, chronic pain, and heart failure.

●Pulmonary disease – Twenty-five to 50 percent of patients with pulmonary disease report insomnia [53,54]. In addition, chronic obstructive pulmonary disease (COPD) symptoms and frequency of acute exacerbation are related to severity of insomnia [55]. The high prevalence of insomnia in this patient population may be related to events that occur when the patient lies down and tries to fall asleep, such as increased work of breathing, pooling of secretions in the airways, and nocturnal bronchoconstriction. Additionally, COPD is associated with increased sympathetic nervous system activity and inflammation, both of which can worsen insomnia. Insomnia may also be related to respiratory stimulant medications or glucocorticoids taken during the night.

●Hypertension – Hypertension and insomnia frequently co-occur [53]. In addition, patients with chronic insomnia have been shown to have increased systolic and diastolic blood pressure during sleep (lack of nocturnal dipping) [56]. Insomnia with and without decreased total sleep time has been associated with an increased risk of hypertension and cardiovascular disease [57-59]. (See 'Cardiovascular risk and mortality' below.)

●Diabetes – Insomnia has been reported in up to one-half of patients with diabetes [53]. This could be due in part to discomfort associated with symptoms such as nocturia, pain from diabetic neuropathy, nocturnal hypoglycemia, or other primary sleep disorders that are increased in patients with diabetes (eg, restless legs syndrome and obstructive sleep apnea) [60].

●Cancer – The prevalence of insomnia in patients with cancer is 30 to 60 percent, depending on the type of cancer [61,62]. Contributing factors may include pain and other physical symptoms, side effects of treatment, emotional distress and psychiatric comorbidities, and the effects of hospitalization. (See "Insomnia in palliative care".)

●Chronic pain – Approximately 75 percent of patients with chronic pain have symptoms of insomnia [63]. Predictors of insomnia in patients with chronic musculoskeletal pain include the presence of widespread pain, physical limitations, and reduced social participation [64]. Even short-term treatment for insomnia can be associated with long-term improvement in sleep, chronic pain, and fatigue [65].

●Heart failure – Approximately 30 percent of patients with heart failure may have insomnia [66]. The insomnia may be related to Cheyne-Stokes breathing or frequent awakenings due to nocturia caused by use of a diuretic. Insomnia and frequent awakenings have also been associated with an increased risk of atrial fibrillation [67,68]. (See "Sleep-disordered breathing in heart failure".)

●Others – Insomnia is observed with increased frequency in patients with rheumatologic disease (eg, arthritis, fibromyalgia), ischemic heart disease, urologic disease (eg, benign prostatic hyperplasia), endocrine disease (eg, menopause, hyperthyroidism), kidney disease, dermatologic disorders (eg, pruritus), and gastrointestinal disease (eg, gastroesophageal reflux).

Neurologic disorders — Insomnia is common in patients with a wide range of neurologic diseases, including epilepsy, primary headache disorders, nerve and muscle diseases, stroke, multiple sclerosis, neurogenetic disorders, neurodegenerative dementias, and movement disorders. As in other medical and psychiatric disorders, multiple factors may contribute to insomnia prevalence in patients with neurologic disorders, including the condition itself, symptoms of the disorder, such as pain or spasticity, medications used to treat the disorder, such as glucocorticoids and certain antiseizure medications, and comorbid sleep disorders such as RLS, circadian sleep-wake rhythm disorders, and sleep apnea.

Risk factors, clinical presentation, and management of insomnia in specific neurologic disorders is reviewed in more detail in the following topics:

●Alzheimer disease and other neurodegenerative dementias (See "Sleep-wake disturbances and sleep disorders in patients with dementia".)

●Parkinson disease (See "Insomnia, daytime sleepiness, and other sleep disorders in Parkinson disease", section on 'Insomnia'.)

●Traumatic brain injury (See "Sleep-wake disorders in patients with traumatic brain injury", section on 'Insomnia'.)

●Epilepsy (See "Comorbidities and complications of epilepsy in adults", section on 'Sleep disorders'.)

●Multiple sclerosis (See "Manifestations of multiple sclerosis in adults", section on 'Sleep disorders'.)

Medication and substances — A variety of medications can be associated with insomnia (table 1). Commonly implicated classes of medications and substances include:

●Central nervous system stimulants, such as caffeine, methylphenidate, amphetamine and modafinil.

●Respiratory stimulants, such as theophylline.

●Appetite suppressants.

●Antidepressants.

•Monoamine oxidase inhibitor antidepressants are associated with insomnia in nearly 70 percent of patients.

•Selective serotonin reuptake inhibitors, such as fluoxetine, are associated with insomnia in 5 to 35 percent of patients.

•Norepinephrine and dopamine reuptake inhibitors, such as bupropion, are associated with insomnia in 5 to 20 percent of patients.

•Serotonin and norepinephrine reuptake inhibitors, such as venlafaxine, are associated with insomnia in 4 to 18 percent of patients.

•Most tricyclic antidepressants are sedating, but some (eg, protriptyline) can produce insomnia.

●Beta blockers, such as propranolol, metoprolol, and pindolol, can produce sleep-onset insomnia, increased awakenings, and dreams.

●Glucocorticoids, such as prednisone and dexamethasone, are associated with increased wakefulness during the night [69]. Insomnia may occur in 50 to 70 percent of patients who receive prednisone.

●Alcohol, caffeine, and tobacco.

●Diuretics, which can cause nocturia and increased awakenings.

●Over-the-counter medications, such as nasal decongestants and cold medicine.

Medications whose withdrawal can cause insomnia include sedatives, hypnotics, and glucocorticoids.

Other sleep disorders — Insomnia symptoms may co-occur with other sleep disorders, especially sleep apnea, restless legs syndrome (RLS), and circadian sleep-wake rhythm disorders.

Sleep apnea — Patients with sleep apnea have pauses in respiration during sleep that are frequently associated with brief arousals when they resume respiration. As a result, they often report frequent awakenings, poor sleep, or daytime deficits. Approximately 30 to 50 percent of people with obstructive sleep apnea (OSA) report insomnia, and conversely, 30 to 40 percent of people with insomnia have OSA [70]. This proportion is even higher in patients with chronic, treatment-refractory insomnia referred to a sleep center; in such patients, the prevalence of sleep-disordered breathing has been reported to be as high as 90 percent [71].

In some cases, the insomnia does not improve despite successful treatment of the sleep apnea, indicating that the insomnia may be a comorbidity and not a consequence of sleep apnea. In these cases, additional therapy for insomnia may be indicated. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults" and "Central sleep apnea: Risk factors, clinical presentation, and diagnosis".)

Restless legs syndrome — RLS is characterized by an urge to move the legs, accompanied by sensations that are variably described as creeping, crawling, itching, or jitteriness in the legs. Symptoms emerge during periods of inactivity and are most prominent in the evening. In a study that included 551 patients with RLS symptoms occurring at least twice weekly, an estimated 88 percent of them reported at least one symptom of sleep disturbance, particularly difficulty falling asleep or waking frequently during the night [72]. (See "Clinical features and diagnosis of restless legs syndrome and periodic limb movement disorder in adults".)

Periodic limb movements of sleep — Periodic limb movements of sleep (PLMS) are repetitive and highly stereotyped limb movements during sleep. They usually involve the legs and occasionally involve the arms. PLMS may be accompanied by partial arousals, causing sleep fragmentation and difficulty maintaining sleep, although there is controversy among clinicians about whether PLMS alone contribute to insomnia in the absence of RLS. (See "Clinical features and diagnosis of restless legs syndrome and periodic limb movement disorder in adults", section on 'Periodic limb movements of sleep'.)

Circadian rhythm sleep-wake disorders — Jet lag causes insomnia with an acute course, which generally resolves after adaptation to the new light-dark schedule. Night shift work is also commonly associated with insomnia, as individuals are attempting to sleep when their circadian rhythm is promoting wakefulness, and it can be chronic in individuals working regular night shifts, extended shifts, or rotating shifts. (See "Jet lag" and "Sleep-wake disturbances in shift workers".)

Intrinsic circadian disorders, such as the more common delayed sleep-wake phase disorder and the less common advanced sleep-wake phase disorder, also manifest with insomnia symptoms due to misalignment of the circadian system with the desired sleep schedule. The key to suspecting an underlying circadian disorder is recognition of abnormal sleep-wake patterns, above and beyond the complaint of insomnia or daytime sleepiness. (See "Overview of circadian rhythm sleep-wake disorders", section on 'Clinical manifestations'.)

ADVERSE OUTCOMES — 

Chronic insomnia has an adverse impact on daytime function, safety, and quality of life. Insomnia with objective short sleep duration is associated with increased cardiovascular risk and mortality.

Quality of life — Patients with insomnia report increased fatigue, sleepiness, confusion, tension, anxiety, and depression compared with controls [18]. Such dysphoria pervades other areas of life, causing patients with insomnia to report a decreased quality of life and degraded performance.

Patients with insomnia have decrements in both medical and emotional aspects of life, as determined by a standard measure of quality of life, the Medical Outcomes Study Short Form (SF-36) [73]. The magnitude of the impairment was similar to that seen in patients with a chronic medical condition (eg, heart failure) or depression. An analysis of data from the 2020 National Health and Wellness Survey of approximately 75,000 adults in the United States found that insomnia severity was associated with worse quality of life, decreased workplace productivity, and increased health care utilization [74].

Quality of life can also be measured by looking at employment measures, such as promotions and sick time. Patients with insomnia are less likely to receive promotions and more likely to have errors or accidents, to be absent from work, and to have more health-related consequences [18,75]. The poor work performance, increased medical issues, and increased emotional burden associated with insomnia increase costs to society [76,77]. Insomnia in older adults is associated with decreased ability to perform household activities as well as valued or enjoyable activities [78].

Accidents and injuries — Individuals with insomnia are at increased risk of accidents at home, at work, and while driving. A cross-sectional survey of over 5000 individuals found that those who reported symptoms of insomnia were significantly more likely to report motor vehicle accidents and accidents at work and home [79].

Cognitive function and performance — Patients with insomnia are almost universally concerned that their poor sleep has negative consequences on their performance of daily tasks and consistently report subjective performance deficits [80,81]. However, patients with insomnia tend to overestimate the magnitude of the performance deficit, just as they tend to overestimate the magnitude of their sleep deficits.

A meta-analysis of 24 studies found small differences in episodic memory, problem solving, and working memory in patients with insomnia compared with controls [82]. No differences were found in general cognitive function, perceptual and psychomotor processes, procedural learning, verbal functions, attention (including alertness, reaction time, selective or sustained attention), and executive function (verbal fluency or cognitive flexibility). However, patients with more severe insomnia, including significant reduction in sleep duration, are at increased risk for cognitive impairment [83].

Self-medication — People with insomnia frequently seek over-the-counter remedies and have an increased risk of substance use [38]. In untreated insomnia patients, approximately one-quarter have tried alcohol as a treatment [84]. Conversely, one-third to two-thirds of alcohol users report insomnia symptoms, and withdrawal from alcohol is associated with significant sleep disruption [85]. (See "Risky drinking and alcohol use disorder: Epidemiology, clinical features, adverse consequences, screening, and assessment".)

Cannabis use as self-medication is also common and carries risk. A 2018 survey of people in the United States and Canada found that 27 percent of adults had used cannabis at least once for medicinal purposes and that 46 percent of those used it for sleep [86]. Cannabis products are not approved for treatment of insomnia, and cannabis withdrawal is associated with decrements in total sleep and sleep efficiency and increases in latency to sleep [85].

Suicidal ideation and behavior — Both insomnia and decreased total sleep time are independent risk factors for suicidal ideation, suicide attempts, and completed suicides across the lifespan [87-89].

Suicidal behaviors are more common among individuals with psychiatric disorders and those with insomnia [89]. While individuals with psychiatric disorders have increased rates of insomnia, suggesting that the association is primarily mediated by underlying psychiatric illness, some studies have found that the association is present even after adjusting for psychiatric comorbidities [90,91]. Other potential contributing factors and mediators that may link insomnia and suicide include serotonergic dysfunction, dysfunctional beliefs and attitudes about sleep, cognitive dysfunction, and medications and substance misuse [92,93]. One study found that treating insomnia in patients with depression and suicidality improved their sleep and decreased suicidal ideation, with the improvement in insomnia independently associated with the reduction in suicidal ideation [94]. (See "Pharmacotherapy for insomnia in adults", section on 'Shared warnings and precautions'.)

Cardiovascular risk and mortality — Insomnia is associated with sympathetic nervous system activation and elevated cardiovascular risk, including hypertension and myocardial infarction [57,58,95-105]. In particular, the combination of chronic insomnia and decreased objective total sleep time has been associated with increased risk for hypertension [97,106,107] and incident cardiovascular disease [58], and patients with insomnia have been observed to have a non-dipping blood pressure pattern at night [56] that can improve with insomnia treatment [108].

Several prospective observational studies have shown an increased risk of cardiovascular disease and, in some cases, overall mortality in patients with insomnia that remains significant after adjusting for potential confounders [58,99,109,110]. A meta-analysis of prospective cohort studies found that both difficulty maintaining sleep and early morning awakening, but not difficulty falling asleep, were associated with an increased risk for developing hypertension [111].

Diabetes — Patients with insomnia and short nocturnal sleep time are at increased risk for diabetes [112]. Meta-analyses of longitudinal studies in over one million adults have found that insomnia is a risk factor for incident diabetes (hazard ratio [HR] 1.40, 95% CI 1.21-1.63) as well as progression from prediabetes to type 2 diabetes (HR 1.59, 95% CI 1.29-1.97) [113,114]. Treatment of insomnia in patients with diabetes has improved both sleep efficiency and glycemic control as measured by HbA1c in at least one study [115].

Cancer — A meta-analysis of eight cohort studies in over 500,000 individuals found a 24 percent increased risk of cancer in those with a history of insomnia [116]. In a separate meta-analysis, insomnia symptoms were associated with an 11 percent increase in the relative odds of lung cancer [117].

Neurodegenerative disorders — People with insomnia are at increased risk for development of dementia [118,119], particularly Alzheimer disease [119], and studies suggest that beta-amyloid and inflammation levels are also increased in those with insomnia [120]. Among individuals with Alzheimer disease dementia, approximately 25 percent have insomnia [121]. Continuing insomnia may contribute to nocturnal agitation, delirium, and wandering, all of which may be related to increased stage 1 sleep and awakenings, which may produce further brain damage. (See "Sleep-wake disturbances and sleep disorders in patients with dementia".)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Insomnia in adults".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topics (see "Patient education: Insomnia (Beyond the Basics)" and "Patient education: Insomnia treatments (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Epidemiology – One-third to two-thirds of adults report insomnia symptoms of any severity, and approximately 10 to 15 percent have chronic insomnia with daytime consequences. Insomnia is especially common in older adults and women. (See 'Epidemiology' above and 'Intrinsic factors and genetics' above.)

●Risk factors and comorbidities – Risk factors for insomnia include older age, female sex, personal or family history of insomnia, social isolation, life stress, chronic pain, psychiatric disorders, chronic medical and neurologic conditions, selected medications, alcohol and substance use disorders, and other sleep disorders (table 1). Successful treatment requires attention to the insomnia itself as well as relevant comorbidities. (See 'Risk factors and comorbidities' above.)

•Psychiatric disorders – Approximately half of patients with chronic insomnia have a psychiatric disorder, and the majority of those with a psychiatric disorder have insomnia. Frequent comorbidities include mood disorders, substance use disorders, and posttraumatic stress disorder. (See 'Psychiatric disorders' above.)

•Medical conditions – High-risk medical conditions for chronic insomnia include pulmonary disease, hypertension, diabetes, cancer, chronic pain, and heart failure. (See 'Medical conditions' above.)

•Neurologic disorders – Neurodegenerative disorders including dementia and Parkinson disease are frequently accompanied by sleep disturbances and chronic insomnia. (See 'Neurologic disorders' above.)

•Medications – Medications and substances contribute to chronic insomnia in many patients. Commonly implicated classes include central nervous system stimulants, certain antidepressants, glucocorticoids, alcohol, tobacco, and caffeine.

•Other sleep disorders – Insomnia symptoms commonly co-occur with other sleep disorders, especially sleep apnea, restless legs syndrome (RLS), and circadian sleep-wake rhythm disorders.

●Adverse outcomes – Insomnia is a significant health problem associated with multiple adverse health outcomes, including psychiatric disorders, neurodegenerative disorders, suicide, self-medication with alcohol and other substances, hypertension, cardiovascular disease, and diabetes. (See 'Adverse outcomes' above.)

ACKNOWLEDGMENT — 

The UpToDate editorial staff acknowledges Donna L Arand, PhD, and Michael H Bonnet, PhD, who contributed to earlier versions of this topic review.