Sounds like a tricky situation. I don't have any special insight into this, but if I was the person drinking heavily I'd probably find it easier to talk about i

Sounds like a tricky situation. I don't have any special insight into this, but if I was the person drinking heavily I'd probably find it easier to talk about it outside the work environment, and I probably wouldn't want to talk about it if I didn't know the other person that well. I guess what I'm saying is that it'll take a friend to help him get through it. If one of your colleagues spends time with him outside work, perhaps they can help you understand what the senior developer is going through. The other option is to cut down on alcohol in the office, but whilst that's the simplest solution it might cause other issues.