But what kills the neurons?

Many scientists have long suspected that the immune system is responsible. That would make narcolepsy an autoimmune disease–one in which a person’s immune system turns on their own healthy cells.

There’s been a lot of evidence to support this idea, but a team of scientists from Stanford University have finally found what they describe as a “smoking gun”. People with narcolepsy, and only people with narcolepsy, have a special group of immune cells that targets hypocretin. These cells might be attacking the neurons directly, or acting through an intermediary, or something else altogether. Either way, it’s the first clear, direct sign of autoimmunity.

The study also helps to explain some puzzling quirks about narcolepsy, like why the 2009