Don Draper is an alcoholic. No, not just in season 4 when it’s portrayed as a negative thing – he’s always been an alcoholic. He has – conservative estimate that he told his doctor – 5 drinks a day on average, but he’s almost always drinking hard liquor.
Though his addiction to cigarettes is discussed, his alcoholism isn’t until it began affecting his life. Alcoholism, though, doesn’t always affect people’s lives in such obvious ways. The idea of a ‘functioning alcoholic’ isn’t new, and it isn’t unique to this show.