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State medical marijuana laws linked to changes in perceived acceptability, risks of marijuana use among adolescents and young adults

A new study examined the relationship between state medical marijuana laws (MMLs) and attitudes and perceptions of marijuana among U.S. young adults. According to the Health Belief Model and Deterrence Theory, attitudes and perceptions influence the perceived severity of consequences associated with a behavior, which is linked to behavioral intention and behavior. This study used a quasi-experimental difference-in-differences design to estimate the policy effect of MMLs (controlling for potential confounders). The authors hypothesized MMLs affected four dimensions of marijuana-related attitude/perception:  (1) Perceived harmfulness of marijuana use, (2) perceived acceptance of marijuana use, (3) perceived wrongfulness of recreational marijuana use, and (4) perceived availability of marijuana. Data from a restricted-access version of the National Survey on Drug Use and Health (NSDUH) from 2004 – 2012 were examined. The final sample for this study was approximately 388,200 responses, which were stratified by age into adolescents (aged 12 – 17 years; N ≈ 191,700) and young adults (aged 18 – 25 years; N ≈ 196,500). The four attitudinal/perception pathways examined in this study were perceived availability of marijuana (dichotomized as very easy/easy vs. difficult/impossible to get), perceived acceptance of marijuana use (perceived parental acceptance for adolescents and peer acceptance for both groups), perceived wrongfulness of recreational marijuana use (none/fine penalty, jail/prison sentence, diversion-program penalty, or punishment uncertain), and perceived harmfulness of marijuana use (no/low risk vs. moderate/high risk). The key independent variable was state implementation of MMLs during the study period. The authors controlled for individual sociodemographic characteristics and time-variant state-level economic and policy environment (e.g., unemployment rate). The authors analyzed the NSDUH data using logistic regressions and converted results into marginal additive effects. Results indicated the proportion of both groups who perceived no/low health risk associated with marijuana use increased from 2004 to 2012, as did personal acceptance of marijuana use, perceived none/fine penalty for recreational use, and past-month among young adults. For both groups, the authors found there was no change in perceived availability of marijuana attributable to state MMLs. For perceived acceptance of marijuana use, results indicated the implementation of MMLs was associated with a 0.37% point (95% CI − 0.72, − 0.03) decrease in the probability that adolescents perceived acceptance of marijuana use from their parents, but no change in personal acceptance of use. No change in perceived wrongfulness of recreational marijuana use was attributable to MML implementation, which the authors inferred suggested residents in MML states were not likely to misinterpret MML implementation as an overall reduction in legal penalty for any marijuana possession. Among young adults, implementation of MMLs was associated with a 4.72% point (95% CI 0.15, 9.28) increase in the probability of perceiving no/low health risk from using marijuana. No significant effects were observed among adolescents for these constructs.

Take away: Findings from this study indicate the implementation of state medical marijuana laws was associated with a significant increase in the probability that young adults perceive no/low health risk from using marijuana.

Wen, H., Hockenberry, J.M. & Druss, B.G. (2018). The effect of medical marijuana laws on marijuana-related attitude and perception among US adolescents and young adults. Prevention Science [published online ahead of print May 16, 2018] doi: 10.1007/s11121-018-0903-8

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