It's all wrong.
On the general "over-diagnosis" of ADHD, my problematic social-darwinist opinion: I believe that especially in the US there might really be more people with ADHD brains (in the end leaving your continent to settle on a new one is still perceived as something bold to do in 2014 - think of how much more risky this must have felt over the first couple of centuries after the discovery of America).
I can also think of many reasons why people are willing to take medication these days - all of them probably boil down to being profoundly desperate. I remember my grandfather who died last year at age 90, he clearly had all the traits of severe ADHD but he also had a secretary (cue "Mad Men" generation) and so didn't need to manage all the minutiae himself and was very successful at his job at a big company fully capitalizing his creative/impulsive side. This is a luxury most people with ADHD don't have any more as we are expected to do a lot more different, often detail oriented little jobs in-between - so to be able to do a somewhat acceptable job with those kinds of tasks it drives people towards drugs like Adderall, Ritalin etc (I'm constantly abusing caffeine myself, it doesn't help much but again I'm desperate). I can't tell you how devastating it feels when people who don't understand our different wiring shout at you to "simply just fucking do it" when you are really, really trying hard to do just that. It's terrible and drives a lot of people towards alcohol and heavy drug addictions. I've read somewhere that a very high percentage of the jail population actually has ADHD.