Narcolepsy is a chronic neurological disorder that affects the brain’s ability to control sleep-wake cycles, causing excessive daytime sleepiness, sleep paralysis, and sleep-related hallucinations. It is a genetic disorder caused by a deficiency in the production of a brain chemical that helps neurons communicate. The main characteristic of narcolepsy is excessive and overwhelming daytime sleepiness, which can cause impairments in school, work, and social settings as well as heighten the risk of serious accidents and injuries.