Diagnostic Features

The essential feature of Primary Insomnia is a complaint of difficulty initiating or maintaining sleep or of nonrestorative sleep that lasts for at least 1 month (Criterion A) and causes clinically significant distress or impairment in social, occupational, or other important areas of functioning (Criterion B). The disturbance in sleep does not occur exclusively during the course of another sleep disorder (Criterion C) or mental disorder (Criterion D) and is not due to the direct physiological effects of a substance or a general medical condition (Criterion E).

Individuals with Primary Insomnia most often report a combination of difficulty falling asleep and intermittent wakefulness during sleep. The specific type of sleep complaint often varies over time. For instance, individuals who complain of difficulty falling asleep at one time may later complain of difficulty maintaining sleep, and vice versa. Less commonly, individuals with Primary Insomnia may complain only of nonrestorative sleep - that is, feeling that their sleep was restless, light, or of poor quality. Not all individuals with nighttime sleep disturbances are distressed or have functional impairment. A diagnosis of Primary Insomnia should be reserved for those individuals with significant distress or impairment.

Primary Insomnia is often associated with increased physiological, cognitive, or emotional arousal in combination with negative conditioning for sleep. A marked preoccupation with and distress due to the inability to sleep may contribute to the development of a vicious cycle: the more the individual strives to sleep, the more frustrated and distressed he or she becomes and the less he or she is able to sleep. Lying in a bed in which the individual has frequently spent sleepless nights may cause frustration and conditioned arousal. Conversely, the individual may fall asleep more easily when not trying to do so (e.g., while watching television, reading, or riding in a car). Some individuals with increased arousal and negative conditioning report that they sleep better away from their own bedrooms and their usual routines. Individuals with Primary Insomnia may thereby acquire maladaptive sleep habits (e.g., daytime napping, spending excessive time in bed, following an erratic sleep schedule, performing sleep-incompatible behaviors in bed) during the course of the disorder. Chronic insomnia may lead to decreased feelings of well-being during the day (e.g., deterioration of mood and motivation; decreased attention, energy, and concentration; and an increase in fatigue and malaise). Although individuals often have the subjective complaint of daytime fatigue, polysomnographic studies usually do not demonstrate an increase in physiological signs of sleepiness.

Associated Features and Disorders

Associated descriptive features and mental disorders. Many individuals with Primary Insomnia have a history of “light” or easily disturbed sleep prior to the development of more persistent sleep problems. Other associated factors may include anxious overconcern with general health and increased sensitivity to the daytime effects of mild sleep loss. Symptoms of anxiety or depression that do not meet criteria for a specific mental disorder may be present. Interpersonal, social, and occupational problems may develop as a result of overconcern with sleep, increased daytime irritability, and poor concentration. Problems with inattention and concentration may also lead to accidents. Individuals with severe insomnia have greater functional impairment, lower productivity, and increased health care utilization compared with individuals without sleep complaints. Individuals with Primary Insomnia may also report interpersonal and work-related stress.

Individuals with Primary Insomnia may have a history of mental disorders, particularly Mood Disorders and Anxiety Disorders. Primary Insomnia also constitutes a risk factor for (or perhaps an early symptom of) subsequent Mood Disorders, Anxiety Disorders, and Substance Use Disorders. Individuals with Primary Insomnia sometimes use medications inappropriately: hypnotics or alcohol to help with nighttime sleep, anxiolytics to combat tension or anxiety, and caffeine or other stimulants to combat excessive fatigue. In some cases, this type of substance use may progress to Substance Abuse or Substance Dependence.

Associated laboratory findings. Polysomnography often demonstrates poor sleep continuity (e.g., increased sleep latency, increased intermittent wakefulness, and decreased sleep efficiency) and may demonstrate increased stage 1 sleep and decreased stages 3 and 4 sleep. Other laboratory findings may include increased muscle tension and increased amounts of alpha and beta activity during sleep as measured by quantitative EEG analysis. These features must be interpreted within the context of age-appropriate norms. Polysomnographic measures often show considerable variability from night to night. Individuals with Primary Insomnia may also have substantial discrepancies between subjective and polysomnographic measures of sleep quantity, most commonly in the direction of underestimating sleep amount. Some individuals may report better sleep in the laboratory than at home, suggesting a conditioned basis for sleep complaints. Individuals with Primary Insomnia typically do not have increased daytime sleepiness as measured by sleep laboratory testing compared with individuals without any Sleep Disorders. Other psychophysiological tests may also show high arousal (e.g., increased muscle tension, excessive physiological reactivity to stress, and increased metabolic rate).

Individuals with Primary Insomnia may also have elevated scores on self-report psychological or personality inventories (e.g., on profiles indicating chronic, mild depression and anxiety; an “internalizing” style of conflict resolution; and a somatic focus). Measures of neuropsychological test performance do not show consistent patterns of impairment among individuals with Primary Insomnia.

Associated physical examination findings and general medical conditions. Individuals with Primary Insomnia may appear fatigued or haggard but show no other characteristic abnormalities on physical examination. There may be an increased incidence of stress-related psychophysiological problems (e.g., tension headache, increased muscle tension, gastric distress).

Specific Age and Gender Features

Survey data consistently demonstrate that complaints of insomnia are more prevalent with increasing age and among women. The increasing prevalence of insomnia complaints with age may be attributable partly to the increased rates of physical health problems in the elderly. Young adults more often complain of difficulty falling asleep, whereas midlife and elderly adults are more likely to have difficulty with maintaining sleep and early morning awakening. Paradoxically, despite the greater prevalence of insomnia complaints among elderly women, polysomnographic studies generally indicate better preservation of sleep continuity and slow-wave sleep in elderly females than in elderly males. The reason for this discrepancy between self-report and laboratory data is not known. Although polysomnographic studies are of limited value in the routine evaluation of insomnia, they may be more useful in the differential diagnosis of insomnia among older adults than among younger individuals. This is because older individuals more often have identifiable etiologies for their sleep complaints, such as periodic limb movements and sleep apnea.

Prevalence

There are few data regarding the prevalence of Primary Insomnia in the general population. Population surveys indicate a 1-year prevalence of insomnia complaints of 30%-45% in adults. The prevalence of Primary Insomnia is approximately 1%-10% in the general adult population and up to 25% in the elderly. In clinics specializing in sleep disorders, approximately 15%-25% of individuals with chronic insomnia are diagnosed with Primary Insomnia.

Course

The factors that precipitate Primary Insomnia may differ from those that perpetuate it. Most cases have a fairly sudden onset at a time of psychological, social, or medical stress. Primary Insomnia often persists long after the original causative factors resolve, due to the development of heightened arousal and negative conditioning. For example, a person with a painful injury who spends a great deal of time in bed and has difficulty sleeping may then develop negative associations for sleep. Negative associations, increased arousal, and conditioned awakenings may then persist beyond the convalescent period, leading to Primary Insomnia. A similar scenario may develop in association with insomnia that occurs in the context of an acute psychological stress or a mental disorder. For instance, insomnia that occurs during an episode of Major Depressive Disorder can become a focus of attention with consequent negative conditioning, and insomnia may persist long after resolution of the depressive episode. In some cases, Primary Insomnia may develop gradually without a clear stressor.

Primary Insomnia typically begins in young adulthood or middle age and is rare in childhood or adolescence. In exceptional cases, the insomnia can be documented back to childhood. The course of Primary Insomnia is variable. It may be limited to a period of several months, particularly if precipitated by a psychosocial or general medical stressor that later resolves. However, approximately 50%-75% of individuals with insomnia complaints have chronic symptoms lasting for more than 1 year, and previous insomnia is the strongest single risk factor for current insomnia. Some individuals experience an episodic course, with periods of better or worse sleep occurring in response to life events such as vacations or stress.

Familial Pattern

The predisposition toward light and disrupted sleep has a familial association. Limited data from twin studies have yielded inconsistent results regarding the importance of genetic factors in Primary Insomnia.

Differential Diagnosis

“Normal” sleep duration varies considerably in the general population. Some individuals who require little sleep (“short sleepers”) may be concerned about their sleep duration. Short sleepers are distinguished from those with Primary Insomnia by their lack of difficulty falling asleep and by the absence of characteristic symptoms of Primary Insomnia (e.g., intermittent wakefulness, fatigue, concentration problems, or irritability). However, some short sleepers are uninformed as to their abbreviated biological need for sleep, and in their attempt to prolong time in bed, they create an insomnia sleep pattern.

Daytime sleepiness, which is a characteristic feature of Primary Hypersomnia, may infrequently occur in Primary Insomnia but is not as severe. When daytime sleepiness is judged to be due to insomnia, an additional diagnosis of Primary Hypersomnia is not given.

Jet Lag and Shift Work Types of Circadian Rhythm Sleep Disorder are distinguished from Primary Insomnia by the history of recent transmeridian travel or shift work. Individuals with the Delayed Sleep Phase Type of Circadian Rhythm Sleep Disorder report sleep-onset insomnia only when they try to sleep at socially normal times, but they do not report difficulty falling asleep or staying asleep when they sleep at their preferred times.

Narcolepsy may cause insomnia complaints, particularly in older adults. However, Narcolepsy rarely involves a major complaint of insomnia and is distinguished from Primary Insomnia by symptoms of prominent daytime sleepiness, cataplexy, sleep paralysis, and sleep-related hallucinations.

Breathing-Related Sleep Disorder, particularly central sleep apnea, may involve a complaint of chronic insomnia and daytime impairment. However, clinically significant sleep apnea is an uncommon finding among otherwise healthy young and middle-aged individuals with chronic insomnia (although it may be more common in the elderly). A careful history may reveal periodic pauses in breathing during sleep or crescendo-decrescendo breathing (Cheyne-Stokes respiration). A history of central nervous system injury or disease may further suggest a Breathing-Related Sleep Disorder. Polysomnography can confirm the presence of apneic events. Most individuals with Breathing-Related Sleep Disorder have obstructive apnea that can be distinguished from Primary Insomnia by a history of loud snoring, breathing pauses during sleep, and excessive daytime sleepiness.

Parasomnias are characterized by a complaint of unusual behavior or events during sleep that sometimes may lead to intermittent awakenings. However, it is these behavioral events that dominate the clinical picture in a Parasomnia rather than the insomnia.

Primary Insomnia must be distinguished from mental disorders that include insomnia as an essential or associated feature (e.g., Major Depressive Disorder, Generalized Anxiety Disorder, Schizophrenia). The diagnosis of Primary Insomnia is not given if insomnia occurs exclusively during the course of another mental disorder. A thorough investigation for the presence of other mental disorders is essential before considering the diagnosis of Primary Insomnia. A diagnosis of Primary Insomnia can be made in the presence of another current or past mental disorder if the mental disorder is judged to not account for the insomnia or if the insomnia and the mental disorder have an independent course. When insomnia occurs as a manifestation of, and exclusively during the course of, another mental disorder (e.g., a Mood, Anxiety, Somatoform, or Psychotic Disorder), the diagnosis of Insomnia Related to Another Mental Disorder may be more appropriate. This diagnosis should only be considered when the insomnia is the predominant complaint and is sufficiently severe to warrant independent clinical attention; otherwise, no separate diagnosis is necessary. Clinical features such as negative conditioning and poor sleep hygiene are more consistent with a diagnosis of Primary Insomnia, whereas clinically significant nonsleep symptoms (e.g., depressed mood, anxiety) and a chronic, severe course of insomnia are more common in individuals with Insomnia Related to Another Mental Disorder.

In clinical settings, polysomnography is not typically useful in the differential diagnosis of Primary Insomnia versus Insomnia Related to Another Mental Disorder.

Primary Insomnia must be distinguished from Sleep Disorder Due to a General Medical Condition, Insomnia Type. The diagnosis should be Sleep Disorder Due to a General Medical Condition when the insomnia is judged to be the direct physiological consequence of a specific general medical condition (e.g., pheochromocytoma, hyperthyroidism, congestive heart failure, chronic obstructive pulmonary disease). This determination is based on history, laboratory findings, or physical examination. Substance-Induced Sleep Disorder, Insomnia Type, is distinguished from Primary Insomnia by the fact that a substance (i.e., a drug of abuse, a medication, or exposure to a toxin) is judged to be etiologically related to the insomnia. For example, insomnia occurring only in the context of heavy coffee consumption would be diagnosed as Caffeine-Induced Sleep Disorder, Insomnia Type, With Onset During Intoxication.

Relationship to International Classification of Sleep Disorders

Primary Insomnia subsumes a number of insomnia diagnoses in the International Classification of Sleep Disorders (ICSD), including Psychophysiological Insomnia, Sleep State Misperception, Idiopathic Insomnia, and some cases of Inadequate Sleep Hygiene. Psychophysiological Insomnia most closely resembles Primary Insomnia, particularly in terms of arousal and conditioning factors. Sleep State Misperception is a condition characterized by complaints of insomnia with a marked discrepancy between subjective and objective estimates of sleep. Idiopathic Insomnia includes those cases with onset in childhood and a lifelong course, presumably due to an abnormality in the neurological control of the sleep-wake system. Inadequate Sleep Hygiene refers to insomnia resulting from behavioral practices that increase arousal or disrupt sleep organization (e.g., working late into the night, taking excessive daytime naps, or keeping irregular sleep hours).

Diagnostic criteria for 307.42 Primary Insomnia

A. The predominant complaint is difficulty initiating or maintaining sleep, or nonrestorative sleep, for at least 1 month.

B. The sleep disturbance (or associated daytime fatigue) causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.

C. The sleep disturbance does not occur exclusively during the course of Narcolepsy, Breathing-Related Sleep Disorder, Circadian Rhythm Sleep Disorder, or a Parasomnia.

D. The disturbance does not occur exclusively during the course of another mental disorder (e.g., Major Depressive Disorder, Generalized Anxiety Disorder, a delirium).

E. The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.