Feature of narcolepsy: (A) Increased sleep time, (B) Decreased REM sleep latency, (C) Increase in muscle tone, (D) None of the above
Answer is B. The hallmark of this disorder is decreased REM latency, i.e. decreased latent period before the first REM period occurs. Normal REM latency is 90-100 minutes. In narcolepsy, REM-sleep usually occurs within 10 minutes of the onset of sleep. The common age of onset is 15-25 years, with usually a stable course throughout life. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 138