All right then. In that case, I think the best thing to do is be patient and avoid giving the impression that he's been cut off. Maybe try to send the message you miss having him in your lives. The rest is up to him As long as he knows his friends and his family will be there for him no matter what, you've met him half way and he can come join you at any time. After that point, only if you believe there are serious problems like verbal or other abuse going on would you want to take further action.

Meanwhile I doubt this is all that related to ADHD. Again, even if it was, you're not a psychologist and can't treat it. Treat him like you would treat anyone else in the same situation.