We estimated time-varying covariates at level-1 of the HGLM model to examine the unique association between changes in parental knowledge and changes in adolescent substance use over a one-year period (i.e., three time points). Parental knowledge was group-mean centered. Results indicated that within-person decreases in adolescents’ tobacco, marijuana, other, and any drug use were significantly associated with increases in parental knowledge across the three time points. Odds ratios ranged from .82 to .86 suggesting that within a given individual, every unit increase in parental knowledge resulted in a 14 to 18 percent decrease in substance use. Increases in parental knowledge did not predict a decrease in adolescents’ alcohol use.
