The Collaborative Study on the Genetics of Alcoholism (COGA), from which the data for this analysis was drawn, is a multi-site investigation of the genetic factors underlying familial transmission of alcohol use disorder and related phenotypes that began in 1989. Descriptions of COGA’s complex methodology have been fully described elsewhere, notably by Nurnberger et al. (2004) and Reich et al. (1998). Briefly, the first phase of COGA recruited families of individuals receiving treatment for AUD at inpatient and outpatient facilities at six sites1 across the United States with the only major restriction for comorbid intravenous drug dependence. Researchers interviewed first-degree relatives of these probands with a highly reliable tool, the Semi-Structured Assessment for the Genetics of Alcoholism [SSAGA] (Bucholz et al., 1994; Hesselbrock et al., 1999). A set of comparison families was also drawn from the same communities as the families recruited through an alcoholic proband. Since 2004, adolescent and young adult relatives in the original families of the subjects (e.g., offspring, grandchildren, nieces and nephews, as well as offspring of comparison families) who had at least one parent interviewed
