I'm sorry for this situation. I'm assuming you are paying all his bills and college. I think you need to give him an ultimatum. He needs to get therapy and stick with it or he can't live in your home and you won't provide money. I know it's harsh and scary for both of you, but you aren't doing him any favors. He most likely is severely depressed, but it's a cycle that is nearly impossible to get out of without help. But you have to make it so he has to sink or swim. You probably should also seek therapy for yourself to get help for codependency. Good luck!