Rule breaking, a major component of externalizing behavior, was found to be significantly affected by race, peer delinquency, and interaction with GABRA2 (Table 1). The level-1 predictors in the model accounted for approximately 13% of the variance in rule breaking t-scores. The first-order effects suggested that race was associated with rule breaking behavior. Namely, non-European American (i.e., African American and Hispanics) adolescents had higher rates of rule breaking behavior compared to European American adolescents. In addition, first-order effects suggested that high levels of peer delinquency were prospectively associated with higher levels of rule breaking behavior 3 years later. No main effects of GABRA2 were observed. However, as hypothesized, there was evidence for a statistically reliable GABRA2 × Peer delinquency interaction. As depicted in Figure2, the simple slope of peer delinquency was statistically significant for both A-carriers (β = 1.27, P < 0.01) and adolescents with the GG genotype (β = 3.85, P < 0.001) although this association was stronger for adolescents with the GG genotype as hypothesized. This suggests that at low levels of peer delinquency, adolescents with the risk
