modialysis, or withdrawal from medications or  substances of abuse. Nightmares frequently
are comorbid with other mental disorders, in cluding PTSD; insomnia disorder; schizophrenia;
psychosis; mood, anxiety, adjustment, and personality disorders; and grief during be-
reavement. 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 behavior disorder, PTSD, and acute
stress disorder, but nightmare di sorder may be independently coded if nightmares preceded
the condition and their frequency or severity necessitates independent clinical attention. The
latter may be determined by asking whether ni ghtmares were a proble m before onset of the
other disorder and whether they continued after other symptoms had remitted. 
Relationship to Internat ional Classification of 
Sleep Disorders
The International Classification of Sleep Disorders,  2nd Edition (ICSD-2), presents similar di-
agnostic criteria fo r nightmare disorder.
Rapid Eye Movement Sleep Behavior Disorder
Diagnostic Criteria 327.42 (G47.52)
A. Repeated episodes of arousal during sleep associated with vocalization and/or com-
plex motor behaviors. 
B. These behaviors arise during rapid eye movement (REM) sleep and therefore usually
occur more than 90 minutes after sleep onset, are more frequent during the later por-
tions of the sleep period, and uncommonly occur during daytime naps.