Our findings have implications for research and prevention. For research, this study provides additional weight to the body of evidence identifying GABRA2 gene variants as moderators of environmental – and intervention – effects on externalizing behavior and alcohol misuse. Our findings underscore the need for more research into the mechanisms that explain associations between GABRA2 variants, environmental responsiveness, and externalizing behaviors. For prevention, our findings suggest that family- and youth-focused interventions such as those delivered via the PROSPER project may have differential effects based on adolescents’ genotypes, and these differential effects may vary with age. Previous findings on PROSPER project effects have shown that the intervention appears more effective in reducing substance use outcomes for youth at behavioral risk (Spoth et al., 2007; Spoth et al., 2013). Our results add to this work by showing that genetic risk may also moderate PROSPER project effects, as youth with the GABRA2 TT genotype, who were at higher risk in the control group, saw greater intervention-led reductions in alcohol misuse compared to youth with A genotypes, especially during early-to-mid-adolescence (ages 13–16), an important
