Objective: The purpose of this study was to investigate a genetic moderation effect of dopamine receptor-4 gene (DRD4) alleles that have 7 or more repeats on the efficacy of a preventive intervention to deter rural African American adolescents' substance use.
Methods: Adolescents (N = 502, M age = 16 years) were assigned randomly to the Strong African American Families-Teen (SAAF-T) program or to a control condition and were followed for 22 months. Adolescents provided data on substance use, and both adolescents and their primary caregivers provided data on intervention-targeted protective parenting practices.
Results: Male adolescents who carried at least one allele of DRD4 with 7 or more repeats who were assigned to the control condition evinced more substance use across 22 months than did (a) carriers of at least one allele of DRD4 with 7 or more repeats who were assigned to SAAF-T or (b) adolescents assigned to either condition who carried two alleles of DRD4 with 6 or fewer repeats. These findings were mediated by DRD4 × SAAF-T interaction effects on increases in intervention-targeted protective parenting practices, a mediated moderation effect.
Conclusions: The results imply that prevention effects on health-relevant outcomes for genetically susceptible individuals, such as carriers of at least one allele of DRD4 with 7 or more repeats, may be underestimated.
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