hypocretin-1 measurement represents the gold standard, excepting associated severe con-
ditions (neurological, inflammatory, infectious , trauma) that can inte rfere with the assay.
A nocturnal polysomnographic sleep study followed by an MSLT can also be used to
confirm the diagnosis (Criterion B3). These tests must be performed after the individual
has stopped all psychotropic medications, fo llowing 2 weeks of adequate sleep time (as
documented with sleep diaries, actigraphy). Short rapid eye movement (REM) latency
(sleep-onset REM period, REM latency less than  or equal to 15 minutes) during polysom-
nography is sufficient to confirm the diagnosi s and meets Criterion B3. Alternatively, the
MSLT result must be positive, showing a mean sleep latency of less than or equal to 8 min-
utes and two or more sleep-onset REM periods in four to five naps.
Associated Features Supporting Diagnosis