It's a tough one. I don't believe it's a disease. I think it's a fairly normal condition that in a much more dangerous and less regulated world that we live in, it was very much a positive. The ADHD kids were the ones who discovered new lands, killed the leopards trying to eat the band, and took care of the bad guys. It becomes a problem when little kids have to sit in a desk 7 hours a day and do detail work. Same with adults.
It is one of he weird paradoxes of modern society. Not one of those who made major advancements in virtually any field is what we would all call "normal". Some passion, some driving force, the ability to integrate concepts drawn from thought across the spectrum, led to the discoveries (and a few accidents along the way) and the ongoing desire to do something out of the normal scope of most people's existence.
Yet the current educational system, for the most part is centered on some statistical "normal" and either pushing those who can't cope up to it or holding those who'd run roughshod over such a paltry standard back.
That McEducation will turn out McPeople, at a predictable standard of mediocrity, but mediocrity isn't what makes people or countries great. It's what happens when participation trophies take the place of 1st, 2nd, and 3rd.