INTRODUCTION — Insomnia is one of the most common medical complaints. It frequently coexists with medical, psychiatric, sleep, or neurological disorders. It may also be associated with acute stress, medication or substance, poor sleep habits, or changes in the sleep environment. The diagnosis of insomnia requires three main components: persistent sleep difficulty, adequate sleep opportunity, and associated daytime dysfunction.
The clinical features, diagnosis, and differential diagnosis of insomnia are reviewed here. The epidemiology, consequences, and treatment of insomnia are discussed separately. (See "Risk factors, comorbidities, and consequences 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".)
TYPES OF INSOMNIA — Insomnia is described as short-term or chronic, depending on its duration [1].
Short-term insomnia — Short-term insomnia, also referred to as adjustment insomnia or acute insomnia, usually lasts a few days or weeks and occurs in response to an identifiable stressor. By definition, symptoms are present for less than three months [1].
Stressors can be physical, psychological, psychosocial, or interpersonal (eg, job loss, death of a loved one, divorce, argument). Symptoms usually resolve when the stressor is eliminated or resolved or when the individual adapts to the stressor. Occasionally, sleep problems persist and lead to chronic insomnia. This may occur due to the development of poor sleep habits during the acute insomnia period.
Chronic insomnia — Insomnia symptoms that occur at least three times per week and persist for at least three months are considered chronic insomnia [1]. In practice, however, most individuals with chronic insomnia report symptoms for many years. Some individuals recall an initial stressful event that triggered insomnia, but others report nearly lifelong symptoms without an identifiable trigger. Night-to-night variability and a waxing and waning course related to psychosocial stressors and psychiatric or medical comorbidities are common.
Chronic insomnia subsumes alternate or historical terms including primary insomnia, secondary insomnia, and comorbid insomnia [1]. Unlike prior versions [2], the third edition of the International Classification of Sleep Disorders (ICSD-3) no longer contains subclassifications for chronic insomnia (ie, psychophysiological insomnia, idiopathic insomnia, inadequate sleep hygiene, and paradoxical insomnia) [1]. These subtypes were eliminated because they were not felt to be reliably reproducible in clinical practice [1].
CLINICAL FEATURES — Patients with insomnia typically complain about difficulty falling asleep and/or staying asleep. Impaired daytime function must also be reported for a diagnosis of an insomnia disorder. In many cases, comorbid psychiatric or medical disorders, medications or substances, or other sleep disorders are also present. However, the presence of comorbid disorders does not preclude the diagnosis and treatment of insomnia.
Difficulty initiating or maintaining sleep — Patients with insomnia complain of poor sleep quality or insufficient quantity due to difficulty initiating sleep, difficulty maintaining sleep, or waking up too early. Importantly, insomnia differs from sleep deprivation in that it occurs despite adequate opportunity and circumstances for sleep.
Patients may describe variable sleep, with one or several nights of poor sleep followed by a night of better sleep. Occasionally, patients may report having minimal sleep for several consecutive nights.
Most well-rested adults fall asleep within about 10 to 20 minutes of attempting to sleep and spend less than 30 minutes awake during the night. By contrast, adult patients with insomnia usually report taking 30 minutes or more to fall asleep (for those with sleep initiation difficulties) or spending 30 minutes or more awake during the night (for those with sleep maintenance difficulties). Early morning awakening is defined as termination of sleep at least 30 minutes prior to the desired wake-up time.
Patients with insomnia tend to overestimate the amount of time it takes them to fall asleep and underestimate their total sleep time when compared with objective data from polysomnography (PSG) or actigraphy. Although objective measures are typically used in clinical trials of insomnia therapies, they are not used routinely in patient care, and ultimately the patient's perception of their sleep problem is the major factor in guiding the evaluation, diagnosis and treatment of insomnia. (See 'Additional testing' below.)
Compromised daytime function — The diagnosis of insomnia disorder requires that sleep difficulties be accompanied by compromised daytime function related to one or more of the following [1]:
●Fatigue or malaise
●Poor attention or concentration
●Social or vocational/educational dysfunction
●Mood disturbance or irritability
●Daytime sleepiness
●Reduced motivation or energy
●Increased errors or accidents
●Behavioral problems such as hyperactivity, impulsivity or aggression
●Ongoing worry about sleep
Patients with chronic insomnia have often developed behavioral or adjustment issues associated with chronic poor sleep. They are often worried that their lack of adequate sleep will result in significant compromise of their ability to function during the day in both social and professional settings. This concern can create a cycle that worsens the insomnia. Specifically, when patients are unable to fall asleep rapidly, they worry about loss of sleep affecting their performance, and this concern increases with time awake and simultaneously decreases the likelihood of falling asleep, while further increasing stress.
Although severe fatigue is commonly reported by patients with chronic insomnia, actually falling asleep at unwanted or unintended times during the day (ie, excessive daytime sleepiness) is uncommon and may be a sign of an alternative or comorbid sleep disorder. (See "Approach to the patient with excessive daytime sleepiness".)
Common comorbidities — Insomnia commonly coexists with psychiatric or medical disorders, other sleep disorders, or use of certain medications or substances. At times, there is a clear temporal relationship between the insomnia and the condition that is known to disrupt sleep, whereas in many cases it is difficult to discern which condition came first (table 1).
Historically, a distinction was made between primary insomnia (ie, insomnia without comorbidities or existing independently from other disorders) and secondary insomnia (ie, associated with a comorbid condition such as depression) [2]. However, as it is often not possible to draw firm conclusions about the association or direction of causality between insomnia and co-occurring conditions, insomnia is no longer considered a secondary condition, and successful treatment requires attention to both insomnia and comorbidities [1].
Risk factors and common comorbidities of chronic insomnia are reviewed in detail separately. (See "Risk factors, comorbidities, and consequences of insomnia in adults".)
Natural history — Insomnia is often a persistent or recurrent condition, with exacerbations connected to medical, psychiatric, and psychosocial stressors [3-7]. The persistent nature of insomnia underscores the importance of interventions that teach patients ways to manage recurrent symptoms over the lifespan.
Risk factors for persistence include older age, female sex, and increased severity of symptoms [6]. In a study of persistence of insomnia symptoms in over 3000 adults, 59 percent of patients with insomnia disorder consistently maintained that diagnosis for five years, while 26 percent of symptomatic patients consistently maintained that criterion for five years, and rates were higher in females [4]. Among self-identified good sleepers aged 35 years and older, more than 25 percent reported at least one episode of acute insomnia per year, and 6 percent developed chronic insomnia during the following year [5].
DIFFERENTIAL DIAGNOSIS — Insomnia should be distinguished clinically from several other common sleep complaints and conditions (table 2).
Short sleep duration — The amount of sleep required to support adequate alertness, performance, and health varies by age and among individuals (figure 1). While most adults require approximately seven to nine hours of sleep per night on average, some otherwise healthy people regularly sleep less than seven hours per night without the need for catch-up sleep to feel refreshed. Such individuals often report a nearly lifelong and/or familial tendency for short sleep duration. Short sleep duration is distinguished from insomnia by the absence of daytime impairment. (See "Insufficient sleep: Definition, epidemiology, and adverse outcomes", section on 'How much sleep do we need?'.)
Chronic sleep insufficiency — Chronic sleep insufficiency or sleep restriction is due to volitional sleep restriction or insufficient opportunity to sleep, whereas insomnia exists despite adequate opportunity and conditions for sleep (table 3). People with sleep restriction accumulate sleep debt over time and will rapidly fall asleep if given the opportunity. This distinguishes them from most patients with insomnia, who may feel fatigued during the day, but are typically unable to fall asleep if given a chance to take a nap. (See "Insufficient sleep: Definition, epidemiology, and adverse outcomes" and "Insufficient sleep: Evaluation and management".)
Delayed sleep-wake phase disorder — Delayed sleep-wake phase disorder (DSWPD) is one of the most common revised diagnoses given to patients referred to sleep specialists for chronic insomnia, especially those with difficulties falling asleep. DSWPD is a circadian sleep-wake rhythm disorder that can be thought of as a pronounced "night owl" circadian preference. The peak prevalence is in adolescence.
Patients with DSWPD have difficulty initiating sleep at conventional or desired times necessary to obtain sufficient nightly sleep because their circadian phase is delayed, often by several hours, in relation to the environmental light-dark cycle. In addition to difficulty falling asleep at night, they experience difficulty awakening in the morning at conventional times.
Patients with prominent sleep initiation complaints should be asked to describe what happens when they are allowed to sleep according to their desired sleep-wake schedule (eg, on weekends or vacations). Individuals with DSWPD will fall asleep and sleep normally if they wait to go to bed until the correct point in their circadian rhythm (often midnight or later). By contrast, patients with sleep onset insomnia typically describe difficulty falling asleep at any time of night.
DSWPD can be confirmed by sleep logs or actigraphy showing a persistently delayed sleep-wake schedule on weekdays and weekends, with curtailment of total sleep time during periods of enforced awakenings. (See "Delayed sleep-wake phase disorder".)
Advanced sleep-wake phase disorder — Patients with difficulty maintaining sleep or early morning awakening associated with insomnia should be differentiated from patients with advanced sleep-wake phase disorder (ASWPD). Patients with ASWPD have a circadian phase that is advanced or shifted earlier relative to the environmental light-dark cycle so that they tend to fall asleep in the early evening (eg, by 7:00 PM) and wake up in the early morning hours (eg, 3:00 to 4:00 AM), even if they have forced themselves to stay awake until the late evening. ASWPD primarily affects older adults.
ASWPD can usually be distinguished from chronic insomnia by asking patients what happens if they allow themselves to go to bed early. While patients with ASWPD fall asleep easily at this time, those with chronic insomnia typically have difficulty sleeping regardless of the time. Patients with insomnia are also more likely than those with ASWPD to report multiple night awakenings, rather than a specific early morning awakening. (See "Advanced sleep-wake phase disorder".)
EVALUATION — Insomnia is a clinical diagnosis established by history and patient report [8,9]. The goals of the evaluation are to characterize the nature and severity of the sleep problem and identify contributing factors and comorbidities that may be relevant to successful treatment (table 2).
Sleep history and sleep diary — The sleep history should elicit a detailed description of the sleep problem (ie, number of awakenings, duration of awakenings, duration of the problem) and sleep times (ie, bedtime, duration until sleep onset, final awakening time, nap times, and nap lengths) over both a 24-hour period and week. It also includes an assessment of any symptoms of disturbed sleep (eg, daytime sleepiness, fatigue), the duration of the symptoms (ie, acute or chronic), and the sleep environment.
Patients who cannot provide an adequate sleep history or who report considerable day-to-day or night-to-night variability should be asked to complete a daily sleep diary for one or two weeks (table 4 and table 5). Sleep diaries record sleep times, sleep problems, and subjective sleep quality, so that the clinician may review the information for diagnosis and to evaluate treatment efficacy without being misled by recall errors.
The sleep history may provide clues about the cause of the insomnia or factors contributing to the insomnia. It can be helpful to ask patients why they feel it is hard to fall asleep or why they wake up, as these questions often elicit important factors such as "not sleepy," pain, or anxiety. Patients with poor sleep hygiene may describe irregular bedtimes and waking times, while patients whose lifestyle is contributing to their insomnia may report exercising, smoking, or drinking alcohol or caffeine shortly before bedtime. When the bedroom environment is responsible for the insomnia, patients may describe recent changes in light, noise, or other distractions in the bedroom. Patients whose insomnia is due to a primary sleep disorder may report symptoms or signs of the sleep disorder (eg, loud resuscitative snoring in obstructive sleep apnea).
Self-report screening tools — Tracking changes in the chronic insomnia diagnostic items (table 6) or with the sleep diary (table 4 and table 5) can be used to characterize insomnia symptom severity and follow symptoms over time.
Alternatively, validated questionnaires can be completed by patients, acknowledging the limitation that these scales and their resulting cut-off values may not always agree with formal diagnostic criteria.
●Pittsburgh Sleep Quality Index (table 7 and table 8) [10]. A global score of more than 5 out of 21 points indicates significant sleep disturbance.
●Sleep problems questionnaire (calculator 1) [11]. Total scores range from 0 to 20, with higher scores indicating more severe sleep disturbances, and scores of 4 or 5 on any single item indicative of clinically significant sleep disturbance.
Contributing factors — Although not required to confirm or exclude a diagnosis of insomnia, all patients should undergo additional evaluation to determine whether the insomnia is associated with another condition, medication, or substance, since these may also need to be a focus of treatment for the sleep complaint (table 1).
Because depression and anxiety in particular are highly comorbid with insomnia, patients should be screened as part of the routine evaluation. The self-report, two-item Patient Health Questionnaire (PHQ-2) (table 9) can be used as a depression screen, and those who screen positive should be interviewed for depression. The interview can be facilitated with the self-administered PHQ-9 (table 10). (See "Screening for depression in adults", section on 'Screening instruments' and "Unipolar depression in adults: Assessment and diagnosis".)
The generalized anxiety disorder seven-item (GAD-7) scale (table 11) or the State-Trait Anxiety Inventory can be used to screen for anxiety in primary care. (See "Generalized anxiety disorder in adults: Epidemiology, pathogenesis, clinical manifestations, course, assessment, and diagnosis", section on 'Assessment and Diagnosis'.)
The history should also probe for symptoms of comorbid sleep disorders, such as sleep apnea and restless legs syndrome. Positive responses about loud or habitual snoring and witnessed pauses in breathing during sleep raise suspicion for obstructive sleep apnea. A single question, "When you try to relax in the evening or sleep at night, do you ever have unpleasant, restless feelings in your legs that can be relieved by walking or movement?" has good predictive power for the diagnosis of restless legs syndrome. (See "Clinical features and diagnosis of restless legs syndrome and periodic limb movement disorder in adults" and "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)
The medication list, including timing of administration, should be reviewed for contributory agents (table 1). Patients should be asked about habits including caffeine intake, tobacco before bed, and alcohol.
Physical examination — Physical examination of patients with insomnia may reveal medical problems such as hypertension that are associated with insomnia. Other examples include excessive oropharyngeal tissue in obstructive sleep apnea, lower extremity swelling in heart failure, and an abnormal mental status in dementia. In many cases, the physical examination will be normal even if the patient has a medical or psychiatric condition that is associated with insomnia (eg, asthma, ischemic heart disease, gastroesophageal reflux, and menopause).
Laboratories — No routine laboratory studies are necessary in the evaluation of chronic insomnia. Selected tests may be indicated based on clinical suspicion of an important comorbidity. As examples, echocardiography, thyroid function tests, blood glucose and hemoglobin A1C measurements, blood urea nitrogen and creatinine levels, or iron studies may be performed if heart failure, hyperthyroidism, diabetes mellitus, renal disease, or restless legs syndrome is suspected, respectively.
Diagnostic criteria — According to the third edition of the International Classification of Sleep Disorders (ICSD-3), insomnia is confirmed when all four of the following criteria are met (table 6) [1]:
●The patient reports difficulty initiating asleep, difficulty maintaining asleep, or waking up too early. In children or individuals with dementia, the sleep disturbance may manifest as resistance to going to bed at the appropriate time or difficulty in sleeping without caregiver assistance.
●Sleep difficulties occur despite adequate opportunity and circumstances for sleep.
●The patient describes daytime impairment that is attributable to the sleep difficulties. This may include fatigue or malaise; attention, concentration, or memory impairment; social dysfunction, vocational dysfunction, or poor school performance; mood disturbance or irritability; daytime sleepiness; motivation, energy, or initiative reduction; errors or accidents at work or while driving; and concerns or worries about sleep.
●The sleep-wake difficulty is not better explained by another sleep disorder.
Chronic insomnia is differentiated from short-term insomnia if the sleep disturbance and the associated daytime dysfunction has existed for three months or longer and occurs at least three nights per week. Chronic insomnia may also be diagnosed in individuals who report a pattern of repeated occurrence for weeks at a time over several years, even though an individual episode may not last a full three months. A diagnosis of "Other Insomnia" is used for patients who complain of difficulty initiating or maintaining sleep but do not meet all of the criteria for either short-term or chronic insomnia. (See 'Types of insomnia' above.)
The degree of sleep disturbance required to assign an insomnia disorder diagnosis is somewhat arbitrary, in that it relies primarily on individuals' subjective sleep complaints [1]. In addition, the degree of sleep disturbance required to cause daytime impairment varies among individuals and across age groups. In general, the degree of sleep disturbance should include either a sleep latency of 20 minutes or more in children and young adults or 30 minutes or more in older adults; or wake periods of 20 minutes or more in children or young adults or 30 minutes or more in older adults. Complaints of early morning awakening are substantiated by termination of sleep at least 30 minutes prior to the desired wake-up time.
ADDITIONAL TESTING — Additional diagnostic testing is not required in most patients. Polysomnography, home sleep apnea testing, or actigraphy may be performed in selected patients based upon the history and physical. In particular, patients who report excessive daytime sleepiness in association with sleep difficulties should be further evaluated for an alternative or comorbid sleep disorder.
Role of polysomnography — Polysomnography is only indicated for an insomnia complaint if another sleep disorder, such as obstructive sleep apnea, is suspected. Clinicians should have a high index of suspicion for comorbid sleep-disordered breathing in patients with chronic, treatment-refractory insomnia and daytime sleepiness. In these patients, the prevalence of sleep apnea may be as high as 90 percent, and screening instruments such as the Berlin questionnaire may lack sensitivity [12]. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults", section on 'Diagnostic evaluation'.)
The multiple sleep latency test (MSLT) is not typically indicated for an insomnia complaint and is only used if narcolepsy is suspected. (See "Quantifying sleepiness", section on 'Multiple sleep latency test (MSLT)'.)
The home sleep apnea test (HSAT) is an alternative to in-laboratory polysomnography that can be used to diagnose obstructive sleep apnea in selected patients. Although most HSATs in use do not actually measure sleep, some newer models have algorithms for estimating objective sleep time (including derived EEG measures in some cases), which may correlate better with risk for medical comorbidities and adverse outcomes in insomnia. (See "Risk factors, comorbidities, and consequences of insomnia in adults".)
Role of actigraphy — Actigraphy is not routinely indicated in the evaluation of chronic insomnia but is an important adjunct to sleep diaries when a circadian sleep-wake rhythm disorder is suspected or when an objective estimate of total sleep time is needed to support clinical decision making [13,14]. (See 'Differential diagnosis' above.)
Actigraphy is a validated method of objectively measuring sleep parameters and average motor activity over a period of days to weeks using a noninvasive accelerometer, worn like a wristwatch. In patients with suspected circadian rhythm sleep-wake disorders, actigraphy data complements self-reported sleep parameters obtained from sleep diaries and provides a substitute for self-reported sleep parameters in patients who cannot reliably complete sleep diaries. (See "Actigraphy in the evaluation of sleep disorders".)
Reasons for referral — Consider referral to a sleep medicine physician when:
●Insomnia does not respond to therapy.
●Patients with insomnia report profound daytime sleepiness or symptoms of other sleep disorders, including sleep apnea, periodic limb movements, narcolepsy, parasomnias, or circadian rhythm sleep-wake disorders [15,16].
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 5th to 6th 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 10th to 12th 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
●Definition – Insomnia refers to insufficient sleep quality or quantity due to difficulty initiating sleep, difficulty maintaining sleep, or waking up too early. Insomnia disorder is diagnosed when sleep disturbances lead to daytime dysfunction. (See 'Clinical features' above.)
●Types of insomnia
•Short-term insomnia, also referred to as adjustment insomnia or acute insomnia, usually lasts a few days or weeks and occurs in response to an identifiable stressor. By definition, symptoms are present for less than three months. (See 'Short-term insomnia' above.)
•Chronic insomnia refers to insomnia symptoms that persist for at least three months. Most patients with chronic insomnia endorse symptoms over many years. (See 'Chronic insomnia' above.)
●Comorbidities – Insomnia commonly coexists with psychiatric or medical disorders, other sleep disorders, or use of certain medications or substances. (See "Risk factors, comorbidities, and consequences of insomnia in adults".)
●Differential diagnosis – Insomnia should be distinguished from several other common sleep complaints and conditions, including short sleep duration, chronic sleep insufficiency (table 3), and circadian rhythm sleep-wake disorders (table 2). (See 'Differential diagnosis' above.)
●Evaluation –Insomnia is a clinical diagnosis (table 6). The goals of the evaluation are to characterize the nature and severity of the sleep problem and identify contributing factors and comorbidities that may be relevant to successful treatment. In addition to a sleep history, patients should be screened for depression and anxiety. (See 'Sleep history and sleep diary' above and 'Self-report screening tools' above.)
A medical history and physical examination should also be performed to determine whether the insomnia is associated with another condition, medication, or substance, since these may also need to be a focus of treatment for the sleep complaint. (See 'Contributing factors' above and 'Physical examination' above.)
●Testing – Additional testing is guided by the history and physical examination but is not required in most patients. (See 'Additional testing' above.)
