This investigation examined the interplay between polygenic influences underlying alcohol dependence (i.e., PRS) and the influence of close friends’ substance use on the development of heavy episodic drinking in adolescents and young adults. Controlling for parental knowledge and the broader network of peer substance use, close friend substance use predicted a higher initial status and a greater rate of increase in heavy episodic drinking between the ages of 15.5 and 21.5 for both males and females. Additionally, PRS predicted a higher initial status and a greater rate of increase in heavy episodic drinking between the ages of 15.5 to 21.5, but only among males. There was no evidence of interaction between PRS and close friend substance use on heavy episodic drinking outcomes.
