COGA is a diverse family-based study whose objective is to identify genetic and environmental factors implicated in the development of AUD and related psychiatric disorders (Begleiter et al., 1995; Bucholz et al., 2017; Reich et al., 1998). Probands were identified through alcohol treatment centers across seven sites in the United States. Probands along with their families were invited to participate if the family was sufficiently large (usually sibships >3 with parents available), with two or more members living in the COGA site’s catchment area. Comparison families were recruited from the same communities. The Institutional Review Board at all data collection sites approved the study, and written consent (and assent for adolescents) was obtained from all participants. The present study made use of data from participants of European or African ancestry, the two largest ancestry groups in COGA, as determined by genetic ancestry principal component analysis. Analytic sample sizes differed across the outcome measures of interest and ranged from 4638 to 5608 in the European ancestry sample (47% male; Mage = 36.26 years, SD = 14.05) and 1215 to 1714 in the African ancestry sample (46% male; Mage = 33.46 years, SD = 11.89).
