Narcolepsy is a sleep disorder that mixes the nervous system's messages about when to sleep and when to be awake. Narcolepsy usually starts during the teen years or early adulthood and continues throughout life.

Narcolepsy may cause:

• Sudden sleep attacks. These may occur at any time during any type of activity, such as eating dinner, driving a car, or carrying on a conversation. These sleep attacks can occur several times a day and may last from a few minutes to several hours.
• Sudden, brief periods of muscle weakness while a person is awake (cataplexy). The weakness may affect specific muscle groups or may affect the entire body. These periods of muscle weakness are often brought on by strong emotional reactions, such as laughing or crying.
• Excessive daytime sleepiness.
• Hallucinations before falling asleep.
• Brief loss of the ability to move when a person is falling asleep or just waking up (sleep paralysis).

Medicines may help prevent sleep attacks and episodes of muscle weakness. But narcolepsy rarely goes away completely.