Diagnostic Features

The essential feature of Sleep Terror Disorder is the repeated occurrence of sleep terrors, that is, abrupt awakenings from sleep usually beginning with a panicky scream or cry (Criterion A). Sleep terrors usually begin during the first third of the major sleep episode and last 1-10 minutes. The episodes are accompanied by autonomic arousal and behavioral manifestations of intense fear (Criterion B). During an episode, the individual is difficult to awaken or comfort (Criterion C). If the individual awakens after the sleep terror, no dream is recalled, or only fragmentary, single images are recalled. On awakening the following morning, the individual has amnesia for the event (Criterion D). The sleep terror episodes must cause clinically significant distress or impairment in social, occupational, or other important areas of functioning (Criterion E). Sleep Terror Disorder should not be diagnosed if the recurrent events are due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition (Criterion F). Sleep terrors are also called “night terrors” or pavor nocturnus.

During a typical episode, the individual abruptly sits up in bed screaming or crying, with a frightened expression and autonomic signs of intense anxiety (e.g., tachycardia, rapid breathing, flushing of the skin, sweating, dilation of the pupils, increased muscle tone). The individual is usually unresponsive to the efforts of others to awaken or comfort him or her. If awakened, the person is confused and disoriented for several minutes and recounts a vague sense of terror, usually without dream content. Although fragmentary vivid dream images may occur, a storylike dream sequence (as in nightmares) is not reported. Most commonly, the individual does not awaken fully, but returns to sleep, and has amnesia for the episode on awakening the next morning. Some individuals may vaguely recall having an “episode” during the previous night, but do not have detailed recall. Usually only one episode will occur on any one night, although occasionally several episodes may occur at intervals throughout the night.

For the diagnosis to be made, the individual must experience clinically significant distress or impairment. Embarrassment concerning the episodes can impair social relationships. Individuals may avoid situations in which others might become aware of the disturbance, such as going to camp, visiting friends overnight, or sleeping with bedpartners.

Associated Features and Disorders

Associated descriptive features and mental disorders. The episode is usually accompanied by yelling, screaming, crying, or incoherent vocalizations. The individual may actively resist being held or touched or even demonstrate more elaborate motor activity (e.g., swinging, punching, rising from the bed, or fleeing). These behaviors appear to represent attempts at self-protection or flight from a threat and may result in physical injury. Episodes that simultaneously include features of sleep terror and sleepwalking can occur. Alcohol or sedative use, sleep deprivation, sleep-wake schedule disruptions, fatigue, and physical or emotional stress increase the likelihood of episodes.

Children with Sleep Terror Disorder do not have a higher incidence of psychopathology or mental disorders than does the general population. Psychopathology is more likely to be associated with Sleep Terror Disorder in adults. Sleep Terror Disorder may occur with an increased frequency in individuals with Axis I disorders, particularly Posttraumatic Stress Disorder and Generalized Anxiety Disorder. Personality Disorders may occur in individuals with Sleep Terror Disorder, especially Dependent, Schizoid, and Borderline Personality Disorders. Elevated scores for depression and anxiety have been noted on personality inventories.

Associated laboratory findings. Sleep terrors begin during deep NREM sleep that is characterized by slow-frequency EEG activity (delta). This EEG activity is most prevalent during stages 3 and 4 NREM sleep, which are concentrated in the first third of the major sleep episode. Therefore, sleep terrors are also most likely to occur in the first third of the night. However, episodes can occur during slow-wave sleep at any time, even during daytime naps. The onset of sleep terror episodes is typically heralded by very high voltage EEG delta activity, an increase in muscle tone, and a twofold to fourfold increase in heart rate, often to over 120 beats per minute. During the episode, the polysomnogram may be obscured with movement artifact. In the absence of such artifact, the EEG typically shows theta or alpha activity during the episode, indicating partial arousal. Individuals with Sleep Terror Disorder may also have abrupt arousals from deep NREM sleep that do not progress to full episodes of sleep terror. Such episodes can include abrupt tachycardia.

Associated physical examination findings and general medical conditions. Fever and sleep deprivation can produce an increased frequency of sleep terror episodes.

Specific Culture, Age, and Gender Features

No reports have provided clear evidence of culturally related differences in the manifestations of Sleep Terror Disorder, although it is likely that the significance and cause attributed to sleep terror episodes will differ between cultures. Older children and adults provide a more detailed recollection of fearful images associated with sleep terrors than do younger children, who are more likely to have complete amnesia or to report only a vague sense of fear. Among children, Sleep Terror Disorder is more common in males than in females. Among adults, the sex ratio is even.

Prevalence

There are limited data on Sleep Terror Disorder in the general population. The prevalence of sleep terror episodes (as opposed to Sleep Terror Disorder in which there is recurrence and distress or impairment) has been estimated at 1%-6% among children and at less than 1% of adults.

Course

Sleep Terror Disorder usually begins in children between ages 4 and 12 years and resolves spontaneously during adolescence. In adults, it most commonly begins between ages 20 and 30 years and often follows a chronic course, with the frequency and severity of episodes waxing and waning over time. The frequency of episodes varies both within and among individuals. Episodes usually occur at intervals of days or weeks but may occur on consecutive nights.

Familial Pattern

Individuals with Sleep Terror Disorder frequently report a positive family history of either sleep terrors or sleepwalking. Some studies indicate a 10-fold increase in the prevalence of the disorder among first-degree biological relatives. The exact mode of inheritance is unknown.

Differential Diagnosis

Many individuals suffer from isolated episodes of sleep terrors at some time in their lives. The distinction between individual episodes of sleep terrors and Sleep Terror Disorder rests on repeated occurrence, intensity, clinically significant impairment or distress, and the potential for injury to self or others.

Sleep Terror Disorder must be differentiated from other disorders that produce complete or partial awakenings at night or unusual behavior during sleep. The most important differential diagnoses for Sleep Terror Disorder include Nightmare Disorder, Sleepwalking Disorder, other parasomnias (see Parasomnia Not Otherwise Specified), Breathing-Related Sleep Disorder, and seizures occurring during sleep. In contrast to individuals with Sleep Terror Disorder, individuals with Nightmare Disorder typically awaken easily and completely, report vivid storylike dreams accompanying the episodes, and tend to have episodes later in the night. The degree of autonomic arousal and motor activity is not as great as that in Sleep Terror Disorder, and recall is more complete. Sleep terrors usually occur during slow-wave sleep, whereas nightmares occur during REM sleep. Parents of children with Sleep Terror Disorder may misinterpret reports of fearfulness and fragmentary imagery reports as nightmares.

Sleepwalking Disorder may be difficult to differentiate from cases of Sleep Terror Disorder that involve prominent motor activity. In fact, the two disorders frequently occur together, and family history commonly involves both disorders. The prototypical case of Sleep Terror Disorder involves a predominance of autonomic arousal and fear, with a lesser degree of motor activity that tends to be abrupt and disorganized. The prototypical case of Sleepwalking Disorder involves little autonomic arousal or fear and a greater degree of organized motor activity.

Parasomnias Not Otherwise Specified include several presentations that can resemble Sleep Terror Disorder. The most common example is “REM sleep behavior disorder,” which also produces subjective fear, violent motor activity, and the potential for injury. Because this occurs during REM sleep, it involves vivid storylike dreams, more immediate and complete awakening, and motor activity that clearly follows dream content. “Nocturnal paroxysmal dystonia” also includes awakenings from sleep with motor activity, but this activity is longer in duration, more rhythmic and stereotyped, and not associated with subjective reports or signs of fear.

Hypnagogic hallucinations, experienced sporadically by many otherwise-asymptomatic individuals, as well as more regularly by those with Narcolepsy, may be associated with anxiety. Their occurrence at sleep onset, vivid images, and subjective sensation of wakefulness differentiate these episodes from sleep terrors.

Rarely, an individual with a Breathing-Related Sleep Disorder may have episodes of awakenings associated with fear and panic that resemble those in Sleep Terror Disorder. The association with snoring, obesity, and respiratory symptoms such as witnessed apneas, an inability to breathe, or choking episodes distinguishes Breathing-Related Sleep Disorder. A single episode of sleep terror can also occur during the slow-wave sleep rebound that follows the abrupt treatment of obstructive sleep apnea syndrome (e.g., following nasal continuous positive airway pressure [CPAP] therapy).

Seizures that occur during sleep can produce subjective sensations of fear and stereotyped behaviors, followed by confusion and difficulty awakening. Most nocturnal seizures occur at sleep-wake transitions, but they may occur during slow-wave sleep. Incontinence and tonic-clonic movements suggest a seizure disorder, but frontal and temporal lobe seizures can produce more complex behaviors as well. An EEG often reveals interictal findings in individuals with sleep-related seizures, but EEG monitoring during nocturnal sleep may be needed for definitive differential diagnosis. Sleep disruption related to seizures should be diagnosed as Sleep Disorder Due to a General Medical Condition, Parasomnia Type. Sleep Disorders Due to a General Medical Condition other than sleep-related seizures may rarely cause unusual behavioral episodes at night. The new onset of abnormal behavior during sleep in a middle-aged or older adult should prompt consideration of a closed Head injury or central nervous system pathology such as tumor or infection.

Sleep terror episodes also may be exacerbated or induced by medications such as central nervous system depressants. If episodes are judged to be a direct physiological effect of taking a medication or substance, the disorder should be classified as a Substance-Induced Sleep Disorder, Parasomnia Type.

Panic Disorder may also cause abrupt awakenings from deep NREM sleep accompanied by fearfulness, but these episodes produce rapid and complete awakening without the confusion, amnesia, or motor activity typical of Sleep Terror Disorder. Individuals who have Panic Attacks during sleep report that these symptoms are virtually identical to those of Panic Attacks that occur during the day. The presence of Agoraphobia may also help differentiate the two disorders.

Relationship to the International Classification of Sleep Disorders

Sleep Terror Disorder is virtually identical to Sleep Terrors in the International Classification of Sleep Disorders (ICSD). Confusional Arousals, which can occur as an independent disorder or in conjunction with Sleep Terror Disorder, are also described in the ICSD. Confusional Arousals are characterized by brief awakenings from slow-wave sleep with confusion, but without terror or ambulation.

Diagnostic criteria for 307.46 Sleep Terror Disorder

A. Recurrent episodes of abrupt awakening from sleep, usually occurring during the first third of the major sleep episode and beginning with a panicky scream.
B. Intense fear and signs of autonomic arousal, such as tachycardia, rapid breathing, and sweating, during each episode.
C. Relative unresponsiveness to efforts of others to comfort the person during the episode.
D. No detailed dream is recalled and there is amnesia for the episode.
E. The episodes cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.
F. 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.