Popular Psychology - An Encyclopedia,

N NARCOLEPSY Narcolepsy is a sleep disorder in which a person in an active waking state shifts abruptly into several minutes of REM sleep, usually with no warning at all. As REM is the sleep stage in which most dreaming occurs, the disorder may be thought of as a sudden intrusion of dreaming sleep into the consciousness of a person who was awake a moment earlier. In addition to excessive daytime sleepiness, the classic symptoms of narcolepsy include cataplexy, a dramatic and sudden loss of muscle tone, often accompanied by paralysis, that is usually brought on by a strong emotion like fear, surprise, anxiety, or even excessive laughter. As narcolepsy involves the onset of REM sleep, this is unsurprising, as REM sleep is usually accompanied by sleep paralysis, or the disinhibition of muscle movement that prevents us from acting out our dreams as they happen.

Narcoleptic episodes are also frequently accompanied by hypnagogic hallucinations, extremely vivid dreamlike images that occur at the onset of sleep, before a person is fully asleep. This little-known phenomenon is actually fairly common in people without sleep disorders, and provides a possible explanatory mechanism for such unusual phenomena as alien abduction experiences, among others. Disturbances of nighttime sleep, including nightmares, leg jerks, tossing and turning, and frequent awakening, are also very common in people with narcolepsy and may explain some of the daytime sleepiness associated with the disorder. Unrelenting daytime sleepiness is usually the first symptom of the disorder noticed, and it leads to irresistible “sleep attacks,” also sometimes called microsleeps, which can last anywhere from thirty seconds or less to more than thirty minutes, and which can occur anytime, no matter how