COGA is a large family-based study that recruited alcohol dependent probands from treatment facilities across seven sites in the United States32,33. Probands and their extended families were invited to participate. Additional individuals and their families were recruited from the same communities using a variety of resources (e.g., dental clinics). Institutional review boards at all sites approved the study, and all participants provided informed consent. All participants were administered a version of the Semi-Structured Assessment for the Genetics of Alcoholism interview (SSAGA; those aged <18 years were administered a child version, the C-SSAGA)34,35. Phenotypic data were available on 16,809 individuals. A substantial portion of the sample (n=12,146) has been genotyped. Because the number of individuals of other ethnicities was small, only EA (n=7,983) and AA (n=3,685) individuals were included in these analyses. As the study was ascertained for alcohol dependence, individuals who reported never drinking alcohol even once in their life were excluded from analyses (n=550). The majority of those individuals reported not ever using other drugs, with the exception of cannabis (n=63). The final analytic sample (n=7,291 EA and 3,132 AA) included those with both genotypic and phenotypic data.
