the age of 18 received an adolescent version of the SSAGA designed for those between ages 12–17 (Bucholz et al., 1994; Hesselbrock et al., 1999). We used data from the interview where participants endorsed the maximum total number of DSM-IV alcohol dependence criteria (i.e., the phenotype on which study probands were initially recruited) in order to capture their maximal phenotypic expression of externalizing behaviors. We included data from all COGA participants to create the discovery phenotype (n = 16,167). Genetic analyses were limited to those with genome-wide data (n = 11,562). A full description of genotyping and quality control is available in the supplementary material (Section 1).
