with several short sleep-wake cycles assessed during a single session. The test repeat-
edly measures the time to daytime sleep on set (“sleep latency”) and occurrence of and
time to onset of the rapid eye movement sleep phase.
mutism No, or very little, verbal response  (in the absence of known aphasia).
narcolepsy Sleep disorder characterized by period s of extreme drowsi ness and frequent
daytime lapses into sleep (sleep attacks). Th ese must have been occurring at least three
times per week over the last 3 mont hs (in the absence of treatment).
negative affectivity Frequent and intense experiences of  high levels of a wide range of
negative emotions (e.g., anxiety, depressio n, guilt/shame, worry, anger), and their be-
havioral (e.g., self-harm) and interpersonal (e.g., depe ndency) manifestations. Nega-
tive Affectivity is one of the five pathological PERSONALITY  TRAIT  DOMAINS  defined in
Section III “Alternative DSM-5 Mo del for Personality Disorders.”
negativism Opposition to suggestion or advice; be havior opposite to that appropriate to
a specific situation or against the wishes of others, including direct resistance to efforts
to be moved.
night eating syndrome Recurrent episodes of night eating, as manifested by eating after
awakening from sleep or ex cessive food consumption afte r the evening meal. There is
awareness and recall of the eating. The night eating is not better accounted for by ex-
ternal influences such as changes in the in dividual’s sleep-wake cycle or by local social
norms.
nightmare disorder Repeated occurrences of extended, extremely dysphoric, and well-
remembered dreams that usually involve effo rts to avoid threats to survival, security