The discovery and replication samples utilized versions of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA)23, 24 to obtain interview-based self-report data on ages of onset and other alcohol-related measures. In the discovery sample, AO-AD was defined as the age at which individuals reported first experiencing three or more of seven DSM-IV alcohol dependence criteria clustering within a 12-month period. Only individuals who were regular drinkers (that is, reported a lifetime history of drinking at least once a month for 6 months or longer) were included. As is the norm for Cox survival modeling, those who did not meet criteria for DSM-IV AD were censored at their age at interview.
