Hi KarinaM
You haven't said what his original concussion injury was - understand if you can't say this due to the personal injury claim - but it might help others here to figure out where his problems stem from.

Also re his addictions - I'm sure you're aware that may be causing some of his problems - of course no teenager, especially in his condition, is willing to admit that or to consider the long term damage. I have personal experience of a close relative who has permanent serious mental health issues due solely to long term indulgence (no other injury or health issues). I don't want to alarm you and I know you'll be doing your best to keep him safe. PM me if you want to discuss anything in private.