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Most people who have narcolepsy have low levels of hypocretin. This is a chemical in the brain that helps promote wakefulness. What causes low hypocretin levels isn't well understood.
Researchers think that certain factors may work together to cause a lack of hypocretin. These factors may include:
Some research suggests that environmental toxins may play a role in triggering narcolepsy. Toxins may include heavy metals, pesticides and weed killers, and secondhand smoke.
Heredity alone doesn't cause narcolepsy. You also must have at least one other factor, such as one of those listed above, to develop narcolepsy.