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The precise causes of narcolepsy remain unclear. Researchers believe that a combination of genetics and a trigger (such as a virus) may alter chemicals that regulate sleep. For example, the neurotransmitter acetylcholine (a chemical involved in the transmission of nerve impulses in the body) appears to be excessively activated in patients with narcolepsy. There may also be a deficiency of the neurotransmitter known as hypocretin or orexin, which modulates activity in the part of the brain known as the hypothalamus, helping to awaken people and keeping them alert.  

Other researchers have found that people who have narcolepsy may have fewer neurons in the brain that affect the transitions between sleeping and waking.

Narcolepsy can strike at any age, but most often develops between the ages of 10 and 25. It affects both sexes equally. Narcolepsy does not typically run in families despite the fact that researchers believe genetics are partially responsible for the condition.