SICK is a new series by Seeker that looks at how diseases actually work inside our body. This week, it profiles narcolepsy.

When you think of narcolepsy, you probably think of people falling asleep at seemingly random times, but it’s actually much more than that. It causes hallucinations, insomnia, sleep paralysis and can be triggered by moments of joy. Oh, and the key to understanding it came from studying man’s best friend.