I wouldn’t be surprised if narcolepsy was more common in folks with ADHD. A lot of people with ADHD have irregular sleep-wake cycles and poor sleep quality, similar to narcoleptics. Maybe the some of the same brain regions are involved? It is an interesting question. I have ADHD, diagnosed as an adult, and I often wonder if I have some degree of narcolepsy as well, though I haven’t been assessed – I have a terrible time waking up, have periods during the day when I can barely keep my eyes open, and I have a burst of energy in the evening.