Nightmare Disorder

Nightmare disorder is a sleep disorder characterized by typically lengthy, elaborate, story-like sequences of dream imagery that seem real and that incite anxiety, fear, or other dysphoric emotions. Nightmare content typically focuses on attempts to avoid or cope with imminent danger but may involve themes that evoke other negative emotions. Nightmares occurring after traumatic experiences may replicate the threatening situation (“'replicative nightmares”), but most do not. On awakening, nightmares are well remembered and can be described in detail. They occur almost exclusively during rapid eye movement (REM) sleep and can thus occur through out sleep but are; more likely in the second half of the major sleep episode when dreaming is longer and more intense.


Prevalence of nightmares increases through childhood into adolescence. 1 to 4% of parents report that their preschool children have nightmares “often” or “always”. Prevalence increases from ages 10 to 13 for both males and females but continues to increase to ages 20-29 for females (while decreasing for males), when it can be twice as high for females as for males. Prevalence decreases steadily with age for both sexes, but the gender difference remains. Among adults, prevalence of nightmares at least monthly is 6%, whereas prevalence for frequent nightmares is 1%-2%. Estimates often combine idiopathic and posttraumatic nightmares indiscriminately.

Risk Factors

Factors that increase early-night REM intensity, such as sleep fragmentation or deprivation, jet lag, and REM-sensitive medications, might facilitate nightmares earlier in the night, including at sleep onset.

Criterion A

Repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve efforts to avoid threats to survival, security, or physical integrity and that generally occur during the second half of the major sleep episode.

Criterion B

On awakening from the dysphoric dreams, the individual rapidly becomes oriented and alert.

Criterion C

The sleep disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.

Criterion D

The nightmare symptoms are not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication).

Criterion E

Coexisting mental and medical disorders do not adequately explain the predominant complaint of dysphoric dreams.



Specify if:

  • During sleep onset
  • With associated non-sleep disorder, including substance use disorders
  • With associated other medical condition
  • With associated other sleep disorder

Specify if:

  • Acute: Duration of period of nightmares is 1 month or less.
  • Subacute: Duration of period of nightmares is greater than 1 month but less than 6 months.
  • Persistent: Duration of period of nightmares is 6 months or greater.

Severity Specifier

Severity can be rated by the frequency with which the nightmares occur:

  • Mild: Less than one episode per week on average.
  • Moderate: One or more episodes per week but less than nightly.
  • Severe: Episodes nightly.

There are key differences in the diagnostic criteria between nightmares and sleep terrors (night terrors), and the table below outlines these differences. It is important to remember that night terrors occur during deep non-REM sleep (EEG shows a slow wave sleep pattern). Night terrors are technically not dreams, but more of a sudden reaction of fear that occurs during the transition from one sleep stage to another.

Sleep Terrors (Night Terrors) vs. Nightmares

Adapted from Barton Schmitt, MD (2007)
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

Individuals who experience nightmares report more frequent past adverse events, but not necessarily trauma, and often display personality disturbances or psychiatric diagnosis. Sleep deprivation or fragmentation, and irregular sleep-wake schedules that alter the timing, intensity, or quantity of REM sleep, can put individuals at risk for nightmares.

Polysomnographic studies show abrupt awakenings from REM sleep, usually during the second half of the night, prior to report of a nightmare. Heart, respiratory, and eye movement rates may quicken or increase in variability before awakening. Nightmares following traumatic events may also arise during non-REM (NREM), particularly stage 2, sleep. The typical sleep of individuals with nightmares is mildly impaired (e.g., reduced efficiency, less slow-wave sleep, more awakenings), with more frequent periodic leg movements in sleep and relative sympathetic nervous system activation after REM sleep deprivation.

  • Sleep terror disorder
  • REM sleep behaviour disorder
  • Bereavement
  • Narcolepsy
  • Nocturnal seizures
  • Breathing-related sleep disorders
  • Panic disorder (nocturnal)
  • Sleep-related dissociative disorders
  • Medication or substance use

Nightmares may be comorbid with several medical conditions, including coronary heart disease, cancer, parkinsonism, and pain, and can accompany medical treatments, such as hemodialysis, or withdrawal from medications or substances of abuse. Nightmares frequently are comorbid with other mental disorders, including PTSD; insomnia disorder; schizophrenia; psychosis; mood, anxiety, adjustment, and personality disorders; and grief during bereavement.

A concurrent nightmare disorder diagnosis should only be considered when in dependent clinical attention is warranted (i.e. Criteria A-C are met). Otherwise, no separate diagnosis is necessary. These conditions should be listed under the appropriate comorbid category specifier. However, nightmare disorder may be diagnosed as a separate disorder in individuals with PTSD if the nightmares are temporally unrelated to PTSD (i.e., preceding other PTSD symptoms or persisting after other PTSD symptoms have resolved).

Nightmares are normally characteristic of REM sleep behaviour disorder, PTSD, and acute stress disorder, but nightmare disorder may be independently diagnosed if nightmares preceded the condition and their frequency or severity necessitates independent clinical attention. The latter may be determined by asking whether nightmares were a problem before onset of the other disorder and whether they continued after other symptoms had remitted.


You can REMember events (i.e. - no confusion, no amnesia) in REM parasomnias!

Comparison of Parasomnias

Parasomnia Type Stage of Arousal Time of Night EEG during event EMG during event Unresponsive during event Autonomic activity Anmesia Confusion post-episode Family history of parasomnias
Confusional Arousal NREM NREM Stage 2-4 Anytime N/A Low Yes Low Yes Yes Yes
Sleepwalking NREM NREM Stage 3-4 First 2 hours Mixed Low Yes Low Yes Yes Yes
Sleep terrors NREM NREM Stage 3-4 First 2 hours Mixed Low Yes High Yes Yes Yes
REM sleep behaviour disorder REM REM Anytime (but more likely later half) Characteristic of REM High Yes High No No (can remember the dreams!) No
Nightmare disorder REM REM Anytime N/A N/A Yes High No No (can remember the dreams!) No