We conducted a series of sensitivity analyses to evaluate the robustness of the rs10482672 finding among European-American participants. First, to test whether the gene-by-intervention interaction was sensitive to the coding of SNP genotypes, we repeated the analysis assuming a dominance model (in which the SNP was coded as 0 or 1 according to the absence or presence of one or more “A” alleles). Results were unchanged (δ=−0.548, p=0.00018). As a further check, because there were few AA homozygotes for rs10482672 (n=5 treated, n=1 control), we excluded these individuals and repeated the analysis. Again, results were unchanged (δ=−.499, p=0.00111). Second, we tested whether the gene-by-intervention interaction was sensitive to whether externalizing psychopathology status was reported by participants as compared to peer informants. Results were similar regardless of the source of outcome information (for self-reports, δ=−0.415, p= 0.00106; for peer-reports, δ=−0.466, p= 0.00670). Third, we repeated analyses with adjustment for site, cohort, and pre-intervention severity-of-risk for externalizing psychopathology, which was found to moderate intervention effectiveness for some outcomes in previous evaluations of Fast Track (e.g., CPPRG 2011). This analysis also included a severity-of-risk by intervention product term (Keller, 2013). Results from this model were unchanged (δ=−0.551, p< 0.00004).
