A sleep disorder characterized by chronic daytime sleepiness with recurrent episodes of sleep occurring throughout the day. Attacks may last from a few seconds to more than an hour. Cataplexy (sudden loss of muscle tone without loss of consciousness) occurs in about 3 quarters of cases. Other symptoms may include sleep paralysis and hallucinations. In narcolepsy, the REM (rapid eye movement) state of sleep is entered into abnormally rapidly. Narcolepsy is often inherited. Treatment usually involves regular naps, along with stimulant drugs to control drowsiness, and antidepressant drugs to suppress cataplexy.


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