Narcolepsy is believed to be genetic. While people with this disorder start falling asleep just about anywhere or any time, other symptoms may not occur for years such as cataplexy, sleep paralysis, and hypnagogic hallucinations.

Only about 25% of these people will experience all 4 of these symptoms. They usually only experience one of these causes but that experience can be very frightening. The excessive daytime sleepiness generally persists throughout life, but sleep paralysis and hypnagogic hallucinations may not.

These symptoms listed above are generally common with narcolepsy, insomnia becomes a real problem. The symptoms of narcolepsy, especially the excessive daytime sleepiness and cataplexy, often become severe enough to cause serious problems in a person's social, personal, and professional life.

One of the common causes of narcolepsy is an area of Chromosome 6 known as the HLA gene. Certain variations in the HLA gene were thought to increase the risk of an auto-immune response to protein-producing neurons in the brain. The protein produced, called hypocretin or orexin, are responsible for controlling the appetite and sleep pattern
People with narcolepsy often have reduced numbers of these protein-producing neurons in their brains.

Approximately 3,000,000 people in the world suffer from narcolepsy, and about 200,000 of those people are Americans. But fewer than 50,000 Americans are actually diagnosised.