orders are differentiable. Nightmares typically occur later in the night, during REM sleep,
and produce vivid, storylike, and clearly re called dreams; mild autonomic arousal; and
complete awakenings. Sleep terrors typically arise in the first third of the night during
stage 3 or 4 NREM sleep and produce either no dream recall or images without an elabo-
rate storylike quality. The terr ors lead to partial awakenings that leave the individual con-
fused, disoriented, and only partially resp onsive and with substantial autonomic arousal.
There is usually amnesia for the event in the morning. 
REM sleep behavior disorder. The presence of complex motor activity during fright-
ening dreams should prompt further evaluation for REM sleep behavior disorder, which
occurs more typically among late middle-age  males and, unlike nightmare disorder, is as-
sociated with often violent dream enactment s and a history of nocturnal injuries. The
dream disturbance of REM sleep behavior diso rder is described by patients as nightmares
but is controlled by appropriate medication. 
Bereavement. Dysphoric dreams may occur during bereavement but typically involve
loss and sadness and are followed by self-refle ction and insight, rather than distress, on
awakening. 
Narcolepsy. Nightmares are a frequent complaint in  narcolepsy, but the presence of ex-
cessive sleepiness and cataplexy differentiates  this condition from  nightmare disorder. 
Nocturnal seizures. Seizures may rarely manifest as nightmares and should be evalu-
ated with polysomnography and continuous video electroencephalography. Nocturnal
seizures usually involve stereotypical motor activity. Associated nightmares, if recalled,