The sample included alcohol dependent (AD) probands and their family members recruited and assessed through seven participating COGA sites, as well as a community sample assessed without regards to their AD status, as described previously30. Experimental protocols were approved by each site's institutional review board, and informed consent was obtained from all participants. Participants were administered the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA), a poly-diagnostic interview33 that assesses DSM-IV psychiatric disorders, including AD. Individuals below age 18 were administered an adolescent SSAGA. The analytic sample consisted of all participants assessed by the SSAGA with EEG coherence and GWAS data available: 8,810 individuals (6,644 of European ancestry and 2,166 of African ancestry) residing in the United States. Demographic characteristics of the full sample (all individuals with genotypic data) and the analytic sample (all individuals with genotypic data and EEG data) are comparable (Supplemental Table 1). 26.3% of the analytic sample met criteria for DSM-IV AD.
