Sleep Terrors

Sleep Terrors (also known as Night Terrors) are a non-rapid eye movement sleep disorder characterized by the repeated occurrence of precipitous awakenings from sleep, usually beginning with a panicky scream or cry. Sleep terrors usually begin during the first third of the major sleep episode and last 1-10 minutes, but they may last considerably longer, particularly in children. The episodes are accompanied by impressive autonomic arousal and behavioral manifestations of intense fear.

Clinical Presentation

During an episode, the individual is difficult to awaken or comfort. If the individual awakens after the sleep terror, little or none of the dream, or only fragmentary, single images, are recalled. During a typical episode of sleep terrors, 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, sweating, dilation of the pupils). The individual may be inconsolable and is usually unresponsive to the efforts of others to awaken or comfort him or her. Sleep terrors are also called “night terrors” or “pavor nocturnus.


The prevalence of sleep terrors in the general population is unknown. The prevalence of sleep terror episodes (as opposed to sleep terror disorder, in which there is recurrence and distress or impairment) is approximately 36.9% at 18 months of age, 19.7% at 30 months of age, and 2.2% in adults.

Criterion A

Recurrent episodes of incomplete awakening from sleep, usually occurring during the first third of the major sleep episode, accompanied by the following:

  1. Sleep terrors: Recurrent episodes of abrupt terror arousals from sleep, usually beginning with a panicky scream. There is intense fear and signs of autonomic arousal, such as mydriasis, tachycardia, rapid breathing, and sweating, during each episode. There is relative unresponsiveness to efforts of others to comfort the individual during the episodes.
Criterion B

No or little (e.g., only a single visual scene) dream imagery is recalled.

Criterion C

Amnesia for the episodes is present.

Criterion D

The episodes cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.

Criterion E

The disturbance is not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication).

Criterion F

Co-existing mental and medical disorders do not explain the episodes of sleep terrors.

There are key differences in the diagnostic criteria between Nightmares and Sleep Terrors (Night Terrors), and the table below outlines these differences.


Sleep Terrors (Night Terrors) Nightmares
Peak age 1-4 years 3-12 years
Prevalence 2% of children 100% of children
Sleep time First 2 hours Last 4 hours
Stage of sleep Stage 3/4 (slow wave sleep) REM-related
Movement Active Little
Autonomic changes Extreme Mild
Recognizes parent No Yes
Can awaken No Yes
Consolable No Yes
Dreams remembered No Yes
Confusion/disorientation Yes No
History of sleep walking Yes No
Difficult to console Yes No
Potential to hurt self/others Yes No

Adapted from Barton Schmitt, MD (2007).

During a typical episode of sleep terrors, there is often a sense of overwhelming dread, with a compulsion to escape. Although fragmentary vivid dream images may occur, a story-like 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. Usually only one episode will occur on any one night. Occasionally several episodes may occur at intervals throughout the night. These events rarely arise during daytime naps.

Sedative use, sleep deprivation, sleep-wake schedule disruptions, fatigue, and physical or emotional stress increase the likelihood of episodes. Fever and sleep deprivation can produce an increased frequency of NREM sleep arousal disorders. A family history for sleepwalking or sleep terrors may occur in up to 80% of individuals who sleepwalk. The risk for sleepwalking is further increased (to as much as 60% of offspring) when both parents have a history of the disorder.

Individuals with sleep terrors frequently have a positive family history of either sleep terrors or sleepwalking, with as high as a 10-fold increase in the prevalence of the disorder among first-degree biological relatives. Sleep terrors are much more common in monozygotic twins as compared with dizygotic twins. The exact mode of inheritance is unknown.


NREM sleep arousal disorders arise from any stage of NREM sleep but most commonly from deep NREM sleep (slow-wave sleep). They are most likely to appear in the first third of the night and do not commonly occur during daytime naps. During the episode, the polysomnogram may be obscured with movement artifact. In the absence of such artifact, the electroencephalogram typically shows theta or alpha frequency activity during the episode, indicating partial or incomplete arousal.

Unlike arousals from REM sleep associated with nightmares, in which there is an increase in heart rate and respiration prior to the arousal, the NREM sleep arousals of sleep terrors begin precipitously from sleep, without anticipatory autonomic changes. The arousals are associated with impressive autonomic activity, with doubling or tripling of the heart rate. The pathophysiology is poorly understood, but there appears to be instability in the deeper stages of NREM sleep. Absent capturing an event during a formal sleep study, there are no reliable polysomnographic indicators of the tendency to experience sleep terrors.

  • Medical: febrile illness, alcohol, sleep deprivation, stress
  • Rule out brain insults, brain gliomas, epilepsy, cardiac insufficiency
  • Medication-induced complex behaviours: hypnotics, neuroleptics, stimulants, anti-histamines and anti-arrhythmics
  • Nightmare disorder
  • Breathing-related sleep disorders
  • REM sleep behaviour disorder
  • Parasomnia overlap syndrome
  • Sleep-related seizures
  • Alcohol-induced blackouts
  • Dissociative amnesia, with dissociative fugue
  • Malingering or other voluntary behaviour occurring during wakefulness
  • Panic disorder
  • Night eating syndrome

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