Examination of the Divergence in Trends for Adolescent Marijuana Use and Marijuana-Specific Risk Factors in Washington State

Purpose As marijuana laws have become more permissive, survey data on adolescents in the United States have shown an increase in marijuana-specific risk factors, particularly in the proportion of youth who do not perceive marijuana use as harmful. Prevalence of marijuana use among youth, however, has changed little. Using representative data from Washington State, which has legalized medical and nonmedical marijuana for adults, we examined two competing hypotheses to account for this divergence in population trends. Methods Data were from 2000 to 2014 biennial Washington State surveys of 10th-grade students. First, we assessed whether associations between marijuana use and marijuana-specific risk factors have weakened over time. Second, we examined whether decreases in alcohol and cigarette use can account for the lack of expected increase in marijuana use prevalence. Results Despite stability in marijuana use prevalence, there were increases in marijuana-specific risk factors of low perceived harm, youth favorable attitudes about use, and perceived community attitudes favorable to use. Associations between marijuana use and marijuana use predictors varied little across time; if anything, the positive association between low perceived harm and marijuana use grew stronger. Decreases in prevalence of alcohol and cigarette use largely accounted for stability in marijuana use during a period when marijuana risk factors increased. Conclusions Decreases in other types of substance use or in the underlying, common risk for substance use may have mitigated effects of increases in marijuana-specific risk factors.