narcolepsy

narcolepsy, a sleep disorder characterized by excessive daytime sleepiness and recurring unwanted episodes of sleep (“sleep attacks”). People with narcolepsy may abruptly fall asleep at almost any time, including while talking, eating, or even walking. The attacks may range from embarrassing or inconvenient to severely disabling, interfering with a person's daily life. An estimated 125,000–250,000 people in the United States have narcolepsy; it occurs about equally in males and females.

Most people with narcolepsy also experience cataplexy, sudden muscular weakness without loss of consciousness, which usually accompanies laughter or anger. Other symptoms, occurring just after falling asleep or upon awakening, include sleep paralysis (a feeling that one cannot move) and vivid hallucinations.

The cause of narcolepsy is not known with certainty, but most people with narcolepsy have low levels of orexin (or hypocretin), a neurotransmitter that promotes wakefulness. In the case of people with narcolepsy and cataplexy, the cause appears to be an autoimmune response that attacks the brain's orexin-producing neurons. There is no cure. Treatment, including regular planned naps and the use of stimulant drugs (e.g., amphetamines) plus antidepressants for cataplexy, can help to control its symptoms.

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