Narcolepsy is a chronic neurological disorder that impairs the ability of the central nervous system to regulate sleep. It is the second leading cause of excessive daytime sleepiness (after obstructive sleep apnea). It is a serious condition requiring medical treatment usually from a sleep disorders specialist.

People with narcolepsy experience excessive daytime sleepiness, and intermittent, uncontrollable episodes of falling asleep during the daytime. Someone who has narcolepsy is prone to falling asleep while engaged in conversation, driving, eating dinner, or at other inappropriate times. The sleepiness occurs in spite of a full night's sleep and may persist throughout the day.

• Cataplexy -- short-lived intermittent muscle weakness
• Hypnagogic hallucinations -- hallucinations while falling asleep or waking
• Sleep paralysis -- paralysis while falling asleep or waking
• Disturbed nocturnal sleep -- waking up repeatedly throughout the night
• Leg jerks, nightmares, and restlessness

Narcolepsy usually begins in the teens or early twenties. The Epworth Sleepiness Scale is often used to help identify excessive daytime sleepiness and this condition and other conditions of excessive sleepiness.

Narcolepsy can be very serious. For example, falling asleep while driving, using machinery, cooking, etc. can be dangerous or even fatal. Narcolepsy also affects:

• Social and professional relationships. People may think that the individual falling asleep or appearing to lose consciousness suddenly while eating, talking, working or shopping is faking or purposely doing so. It is not uncommon for a narcoleptic to be misinterpreted as lazy or rude.
• Intimate relationships. Extreme sleepiness may cause low sex drive and impotence, adding further complications to your relationship.
• Memory and attention. Some studies report that people with narcolepsy have problems with memory and attention. Excessive tiredness may be contributory.

Typically, a combination of medication and lifestyle treatments are used to treat narcolepsy.

Ideopathic hypersomnolence is similar to narcolepsy, except that sleepiness is often milder and more chronic. Adjunct symptoms of narcolepsy (e.g., cataplexy and sleep paralysis) are absent. Treatment is often similar.