Externalizing and the subscales of rule breaking and aggression at age 15–17 years old were analyzed in separate models and GABRA2 SNP rs279826 was included as a predictor. Adolescent biological sex and race were also included as control variables. Of interest was one-two-way interaction (GABRA2 × peer delinquency) to assess how peer delinquency may interact with genetic susceptibilities to predict externalizing behavior, aggression, and rule breaking 3 years later. To eliminate nonessential multicollinearity, first-order terms (i.e., covariates and peer delinquency) were standardized. GABRA2 SNP rs279826 was dummy coded (0 = A-carriers, 1 = GG) prior to forming the cross-product interaction term as recommended (Aiken and West 1991).
