In conclusion, this study provides further evidence for the long allele of DRD4 increasing susceptibility to peer influences on alcohol use in adulthood. It suggests that this G × E interaction emerges developmentally in young adulthood, but not in adolescence or emerging adulthood, and is more prominent for total alcohol consumption compared to heavy episodic drinking. The findings suggest that young adults with the long allele of DRD4 may benefit from interventions designed to help them reduce affiliations with heavy drinking friends or learn strategies to resist peer influences on alcohol use.
