I've dealt with all types in the musical situations I've been in, but luckily, I've avoided the illicit substance abuser, at least as far as any long-term project goes. However, I played for years in a band with a singer who went off the rails in his personal life about half way through. I think he always had some serious mental issues that he was good at hiding, but once he got divorced from his third wife, his life went crazy. He hit the bottle pretty hard, could no longer keep down a day gig, started dating crazy bar skaggs and groupies, showed all kinds of erratic behavior on stage, vocals were often terrible because he wasn't taking care of his voice anymore, has gotten arrested a few times, etc.
We had a number of Come To Jesus meetings with him, but nothing ever stuck. It all culminated one night after a gig in which our guitarist, who is otherwise a very nice guy, threw singer into the side of his car. We parted ways with that singer then and continued with another vocalist.
If you care about someone, then you should get them help. On the other hand, I've learned that you can't control other people's behavior and you can't take responsible for their behavior either. Sometimes a split is the only viable option: either that person splitting from you or you splitting from them.
We had a number of Come To Jesus meetings with him, but nothing ever stuck. It all culminated one night after a gig in which our guitarist, who is otherwise a very nice guy, threw singer into the side of his car. We parted ways with that singer then and continued with another vocalist.
If you care about someone, then you should get them help. On the other hand, I've learned that you can't control other people's behavior and you can't take responsible for their behavior either. Sometimes a split is the only viable option: either that person splitting from you or you splitting from them.