What causes narcolepsy?

Narcolepsy is the disorder where people fall asleep repeatedly during the day and there seems to be genetic component to this. Luckily there are drugs which can be used to treat it. There can be frightening aspects to narcolepsy, for instance people have been known to suddenly fall down as they fall asleep, or have nasty hallucinations as they fall asleep. The brain chemistry behind it is better understood now, and we do know about the genes that are linked to this. One particular chemical is a substance called hypocretin, and people with narcolepsy tend to have problems with the receptors for this brain chemical, or an abnormal form of this chemical. There are also people with 'clock' genes that give them a faster or slower body clock, but this shouldn't be mistaken for narcolepsy.