Analyses were designed to assess the extent to which a teen's future levels of substance use could be predicted from baseline levels of peer substance use, after controlling for baseline levels of teen substance use. This approach of predicting the future level of a variable while accounting for predictions from initial levels (e.g., stability), yields one marker of change in that variable: increases or decreases in its final state relative to predictions based upon initial levels (J. Cohen & Cohen, 1983). Analyses focused upon the question of whether predictions from baseline peer substance use to future teen substance use would be stronger for some teens than for others (i.e., would teen characteristics moderate the predictive strength of peer substance use on their own future changes in substance use).
