The goal of this study was to identify genetic variants associated with alcohol-related phenotypes. All families were reviewed and the genetically most informative subset of COGA families that could be used for analyses of a variety of alcohol-related phenotypes, including DSM-IV symptom count (SC), were selected for a family-based GWAS. Prioritization in selecting subjects for analysis was based on a higher number of AD family members, the number of relatives who supplied DNA, as well as the number of family members with another key COGA phenotype, electrophysiology measures. To reduce the heterogeneity in the sample, only families that were primarily of Caucasian descent were selected for genotyping, yielding a total of 2322 subjects from 118 extended families who were genotyped. The resulting dataset includes multi-generational families affected by AUDs with an average of 20 subjects per family (Figure S1). After genotype quality control and cleaning, correcting pedigree inconsistencies, and processing the phenotypes (see below), 2010 genotyped individuals were included in the subsequent analyses. Full details on the genotype cleaning are included in the supplementary information.
