Nightmare Disorder

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.

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.

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.

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.