I met a friend in college with real ADD. The type where the medication he takes is about 2 chemical reactions away from straight-up cocaine. One day, he forgot to take his meds, and I was talking to him at lunch. He was in the middle of a sentence, and he just... stopped. Completely frozen. Motionless, mid-gesture, staring off into space. He stayed like this for close to a full minute, and just as I was about to ask him if he was ok, he yelled out "SHIT, WHERE'D IT GO!?!" Apparently the sentence he was saying evaporated from his head while he was in the process of speaking it.

So yeah, there really is such a thing as ADD. I won't contest that it's overdiagnosed to hell and back. I wouldn't be surprised if only 1 case in 100 is the real thing, or even 1 in 1,000. But there actually is a real thing, that exists, underneath all the misdiagnoses.