I think both you and ickplant's reaponse to your comment are correct - it has got a genetic element but even a kid "born with an ADD brain" should be able to "recover" from that pr avoid problems with it in the right environment and with the right events. A lot of us probably only had enough problems with ADD when we were teens or adults, right? Hearing Dr K (healthygamersGG) talk about it in this light is one of the things that helped me understand it properly - he says people can pass the criteria for ADD one year and then "recover from it" later as their brain is growing.

That said I did see a cool video from a psych who seemed to be presenting the opposite idea, yesterday:

https://www.youtube.com/watch?v=UWnJ4wjVu9k

So I came away with the same reaction as you, but his examples gave me food for thought. Especially relevant is the fact he said his kids were completely restless