Narcolepsy is a neurological sleep disorder in which the individual has an uncontrollable desire to fall asleep. Narcolepsy patients sleep as much as a normal person, the only difference is they are powerless to control their sleep timings. Recent research indicates that narcolepsy may be caused by the deficient production of a chemical called 'hypocretin' in the brain.

These sleep attacks occur as brief episodes and may take place even in the most stimulating circumstances, like while driving or talking to a person. Research has shown that narcoleptics are more accident-prone and may also have some difficulty with interpersonal relationships.

In addition to excessive sleepiness the person can suffer from abnormal REM sleep phenomenon like:

Cataplexy

Dreams

Sleep paralysis

It is estimated to be the second leading cause for daytime sleepiness after obstructive sleep apnea.