Well, I can say that alcohol does something for my aexh that it does not do for me. I am both sorry and relieved that I don't really understand. I have a compulsive disorder and his drinking seemed to have the same sort of tone: never entirely a matter of choice.
He described himself to me initially as a "borderline alcoholic." I'm not sure there is such a beast. In my life I have seen one person go through a period of moderate-to-heavy drinking in her 30s or early 40s and then simply cut back and be fine, but he doesn't seem to have that in him.