A one-way analysis of covariance (ANCOVA) was computed on the four Genetic Risk × Prevention Condition groups to test the gene × environment hypothesis. Results of the ANCOVA revealed a significant group effect, F(1, 411) = 5.05, p < .002, effect size = .19. Tukey post hoc tests indicated, as predicted, that youth at genetic risk in the control condition (M = 1.13) evinced greater increases from ages 11 to 14 years in the frequency of past-month risk behaviors than did youth at genetic risk in the SAAF condition (M = 0.30) and youth not at genetic risk in either the control (M = 0.33) or the SAAF (M = 0.22) condition; all ps < .025. Figure 1 illustrates these findings, which support the proposition that participation in an efficacious family-centered preventive intervention can ameliorate genetic risk for preadolescents’ involvement in risk behaviors.
