parameters (i.e., intercepts and slopes) were regressed on to the standardized residual values for close friend substance use, PRS and their interaction, controlling for the standardized residual values for parental knowledge and school substance use. Results from this analysis was consistent with fully saturated non-residual model (Supplemental Table 4). That is, the interaction between PRS and close friend substance remained non-significant, including after accounting for the presence of a gene-environment correlation.
