I have several autistic friends who function just fine. One is even in the military! I can't imagine the autistic children I knew in elementary school who screamed and had violent reactions to everything growing into these calm, completely functional adults that are friends with me today. But I hope wherever the ones I saw in elementarty school are, they are leading happy, fulfilling lives, just like my friends. Actually, I met one of my friends in the sixth grade, and never knew she was autistic until I showed up at her house one day and found her wrapped up in the futon matress, her husband sitting on her. Apparently, being in a "clausterphobic situation" calms her down. Wow.
My significant other has a really, really bad case of ADHD. It took me months to notice. In fact, I wasn't sure, and had to ask. One day I noticed that wherever my S.O. was, all the electronics would be on, several mangas and novels would be out, and of course, we'd be talking. That's when I finally asked and found out what their childhood was like, and how drug therapy was extremely helpful and got my S.O. through his schooling, but that now my S.O. just kind of gives into it and plays two video games, watches TV, reads two or three things, chats online, on the phone and with me pretty seamlessly. I asked if the ADHD interferes at work (my S.O. is in the military) and the answer was that it can be hard to concentrate some days, and others it is easier to control.
Apparently, drugs were an immediate help, but martial arts training was a more permanent solution.