I'm no behavioral scientist, but I've believed for some time that what we call ADD is the result of all the stimulation from TV and other electronic baby sitters while the brain is still being "hard wired" in early childhood development.
Before I had kids I thought the very same thing about ADHD: it was bad parenting, TV, etc. Then I had my oldest. His doctor has already suggested that he's most probably ADHD (without all the testing, so obviously it's just a blatant guess). He watched NO TV until he was three, then just 30 minutes a day at the most. Many days he watched none. When he was allowed to watch, it was Mr. Rogers Neighborhood. Not exactly a bright, flashy, constantly changing attention program. This past March, he and his little brother lost their TV priviledges. Six months later (long, long story), when they were finally allowed to watch TV there had been no difference in his "ADHD-type" behavior.
I am a SAHM who homeschools. My kids don't know what a gameboy is. They spend very little time with computer software. What time they do spend is with educational programs. Still, ny oldest is "hyper". There is an obvious difference between my 5yo and others his age. Anyone who's spent any time around him and other 5yo boys can see it.
Before becoming a parent, I knew that ADHD was the result of bad parenting: ignoring the kids, abusing them, lax disclipline, letting them watch too much TV, bad values, whatever. After living through five years of my oldest, I've had to change my tune. Does my kid have ADHD? I have no idea and I have no plans to pursue that information. I do know, however, that were he in a classroom with twenty other agemates, he'd be the problem kid that made the teacher's life miserable. (BTW, to give a complete picture of my kid, last Friday while sitting on the floor of our kitchen, he easily grasped the concept of multiplication as I was demonstrating the concept of addition to his little brother.)