In the base model, only intercepts and slopes terms were estimated, separately for males and females. The mean initial heavy episodic drinking status (i.e., at age 15.5) significantly differed from zero for both males (b = 1.83, S.E. = .02, p < .0001) and for females (b = 1.52, S.E. = .02, p < .0001). For both sexes, heavy episodic drinking exhibited a positive trajectory from age 15.5 to 21.5 (males: b = .20, S.E. = .01, p < .0001, females: b = .18, S.E. = .01, p < .0001) and a slight negative trajectory from age 23.5 to 27.5 (males: b = −.08, S.E. = .01, p < .0001, females: b = .10, S.E. = .01, p < .0001). In the second model, parental knowledge and school substance use prevalence were included as covariates while close friend substance use and PRS were included as main effects to predict intercepts and slopes for male and female heavy episodic drinking (Table 2). For both sexes, close friend substance use prevalence strongly predicted a higher initial status of heavy episodic drinking and
