My 39yo son has ADHD ....and those here who don't believe this is a disease don't know what they are talking about...
Oh, it's real enough. I worked with a directional driller who had it, and got pretty good at steering him back on topic. He was off his meds, they were 1000 miles away and the doctors wouldn't give him more until those ran out. It was a bit like chasing ricochet rabbit in a discussion, but just a little patience and you found out the guy was excellent at his profession (one of the best I have worked with).
Edited to add: That said, I have serious doubts that it is
as prominent as educators and others stuffing kids wholesale into the category would have us believe. One of the problems with being bright as a kid is that you get easily bored. At that point, it takes self-discipline, and a lot of it, to sit still when in captivity (classroom, meeting, what have you), and for those who don't really have the disorder, that is a learned behaviour. If those kids are medicated into submission inappropriately, they will lack the skills they should have developed when they were young when they get older.