Rapid Eye Movement Sleep Behavior Disorder 407
are often repetitive in nature or reflect epilept ogenic features such as the content of diurnal
auras (e.g., unmotivated dread), phosphenes, or  ictal imagery. Disord ers of arousal, espe-
cially confusional arousals, may also be present.
Breathing-related sleep disorders. Breathing-related sleep disorders can lead to awaken-
ings with autonomic arousal, but these are not usually accompanied by recall of nightmares. 
Panic disorder. Attacks arising during sleep can produce abrupt awakenings with au-
tonomic arousal and fearfulness, but nightmares are typically not reported and symptoms
are similar to panic attacks arising during wakefulness. 
Sleep-related dissociative disorders. Individuals may recall actual physical or emo-
tional trauma as a “dream” during elec troencephalography-documented awakenings.
Medication or substance use. Numerous substances/medicat ions can precipitate night-
mares, including dopaminergics; beta-adrener gic antagonists and other antihypertensives;
amphetamine, cocaine, and other stimulants; antidepressants; smoking cessation aids;
and melatonin. Withdrawal of REM sleep–su ppressant medications (e.g., antidepressants)
and alcohol can produce REM sleep rebound accompanied by nightmares. If nightmares
are sufficiently severe to warrant independent clinical attention, a diagnosis of substance/
medication-induced sleep disorder should be considered. 
Comorbidity
Nightmares may be comorbid with several medical conditions, including coronary heart
disease, cancer, parkinsonism, and pain, and ca n accompany medical treatments, such as he-
modialysis, or withdrawal from medications or  substances of abuse. Nightmares frequently