DNA was extracted from immortalized cell lines, blood, or saliva. A total of 1,350 single nucleotide polymorphisms (SNPs) selected from 130 candidate genes and 186 ancestry informative markers (AIMs) were genotyped using the Illumina GoldenGate Assay platform (Illumina, Inc., San Diego, CA) for 3,443 subjects, a subset of the aggregate sample used in the phenotypic analysis. The AIMs were used to assign ancestry coefficients and thereby identify each subject’s primary ancestry. As described previously, the 130 candidate genes were selected on the basis of their roles in functional domains important in the addictions and in the commonly co-occurring phenotypes of anxiety and depressive disorders [Hodgkinson et al., 2008].
