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Narcolepsy is a disease that causes excessive sleepiness. People with narcolepsy tend to fall asleep several times a day, even though they get enough sleep at night. The cause of the disease is unknown, but much evidence indicates that it is hereditary. Doctors can help ease the problem with drugs, but narcolepsy cannot be cured.
Narcolepsy has several symptoms in addition to excessive sleepiness. For example, narcoleptics may experience episodes (attacks) in which they are awake but cannot move. This condition is called cataplexy. Most episodes are brought on by strong emotions, especially anger or laughter, and last two minutes or less. A person with narcolepsy may also experience sleep paralysis and hypnagogic hallucinations. In sleep paralysis, the person suddenly becomes unable to move just as he or she is falling asleep. Hypnagogic hallucinations are vivid, realistic dreams that occur at the start of sleep.
Scientists believe the symptoms of narcolepsy are related to REM (Rapid Eye Movement) sleep, the phase of sleep during which people dream. The eyes move rapidly during this phase, and the body is paralysed while dreaming occurs. Narcoleptics experience this same sort of paralysis--while awake--during a cataplectic episode. In addition, narcoleptics tend to have REM sleep at abnormal times, especially at the very beginning of sleep. In these cases, the REM dreams may be experienced as hypnagogic hallucinations.
Not all people who are abnormally sleepy have narcolepsy. But if they also experience
cataplexy, they are almost certain to have narcolepsy.
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