I have a friend who I've known for a few years. He drinks heavily, but doesn't get drunk very often. He is successful in his career but I'm aware that there are things in his personal life that he's not happy with. He drinks a lot by himself at home and makes passing comments like saying he's trying to escape. In my opinion he seems depressed and the drinking helps (so he thinks). Since he doesn't get drunk, and it doesn't affect his work at all, how can I have a conversation with him that it's still not a healthy practice?