To better understand the role of genetic propensity and peer use in the longitudinal course of cannabis use, we used data on 1,167 individuals of European descent who were part of a large longitudinal study of the genetics of addictions. We first identified trajectories of cannabis use frequency, and then examined whether trajectory class membership was related to (a) cannabis use PRS and/or (b) perceived peer cannabis use when the subject was 12–17 years old. We also examined whether the relationship between polygenic risk, perceived peer use and trajectory membership could be explained by an interaction model where perceived peer use moderated the influence of polygenic risk on trajectory membership. Results from these analyses can provide a framework for how genetic liability and peer use might interface to shape the developmental unfolding of cannabis use.
