Narcolepsy /ˈnɑrkəˌlɛpsi/, also known as hypnolepsy, is a chronic neurological disorder involving the loss of the brain's ability to regulate sleep-wake cycles normally.[1] People with narcolepsy experience frequent excessive daytime sleepiness, comparable to how non-narcoleptics feel after 24 to 48 hours of sleep deprivation,[2] as well as disturbed nocturnal sleep which often is confused with insomnia. Narcoleptics generally experience the REM stage of sleep within 5 minutes of falling asleep, while non-narcoleptics do not experience REM in the first hour or so of a sleep cycle[3] until after a period of slow-wave sleep unless they are significantly sleep deprived.[4] Another common symptom of narcolepsy is cataplexy, a sudden and transient episode of muscle weakness accompanied by full conscious awareness, typically (though not necessarily) triggered by emotions such as laughing, crying, terror, etc.[5]affecting roughly 70% of people who have narcolepsy.[6]

The term narcolepsy derives from the French word narcolepsie created by the French physician Jean-Baptiste-Édouard Gélineau by combining the Greek νάρκη (narkē, "numbness" or "stupor"),[7][8] and λῆψις (lepsis), "attack" or "seizure".[9]