I guess most people will be able to relate to what I am about to write--even if you did not attend college. When I was in college, drinking was just another way of passing the time: class, study, ballgame, party/drink...
Nobody worried about how much anyone had the night before at the party after the football game. In fact, the ability to "hold your liquor" was looked at as a great quality. Anyway, a few years after college I met one of the guys we used to party with in college. He told me he was going through alcoholism and depression treatment. He had been diagnosed with depression when he was in high school.
He went on to tell me he had never drank when he was in high school, and the reason he drank in college was it made him feel better, at least while he was partying. He also said he would feel lousy the next day and days after, but that was his way of coping.
When we were in college we just thought he was a wild party animal. Anyway, for him, the depression came before the alcoholism and the alcoholism stemmed from the depression.