I think both. I have family that has alcoholic genes so thick that even those that never were around the drunk member are more likely to be a drunk than not. In fact, my little cousin is now drinking twice to three times a week to excess. His father was in full recovery before he hit four. His granddad was a drunk kicked out of the house by the time his oldest son was five, yet my cousin's aunt and uncle died of alcohol related incidents. This one family line is just so well known for their alcoholic gene that they are all now taught to be on the lookout for it and guess what? For the first time, they are starting to see some progress in breaking the patterns.
Clearly behavior-mod is doing something to help them stop but it is not enough. There are times where I do believe there is genetic predisposition to abuse of alcohol. In fact, I have always thought it was one of those things we all kinda want...just some of us have a funky gene that takes that too far...until we become beloved cousin L, who you loved even when he drunk dialed you because he such a wonderful man--until he died at 45 from falling down drunk.