The design of medical marijuana laws and adolescent use and heavy use of marijuana: Analysis of 45 states from 1991 to 2011

- Crude current marijuana and heavy marijuana use rates higher in medical marijuana law (MML) states.
- Decreased odds of current marijuana use with MMLs with state fixed effects.
- Decreased odds of current marijuana use with years since MML enactment.
- Increased odds of current marijuana use with higher possession limits.
- Increased odds of current marijuana use with a voluntary patient registration.

ObjectivesTo assess the association between U.S. state medical marijuana laws (MML), the most liberal category of marijuana policies before legalization, their specific provisions, and adolescent past-30-day use and heavy marijuana use.MethodsThis quasi-experimental study used state Youth Risk Behavior Survey (YRBS) data collected during 1991-2011 from 45 states (N = 715,014) to examine MML effects, taking advantage of heterogeneity across states in MML status and design. Multiple logistic regression modeling was used to adjust for state and year effects, and youth demographics.ResultsUnadjusted analyses found that MMLs were associated with higher rates of adolescent past-30-day marijuana use (odds ratio [OR] = 1.08, 95% confidence interval, [(CI) = 1.03,1.13]) and heavy marijuana use (OR = 1.12, [CI = 1.05,1.21]). However, analyses adjusting for state/year effects found a 7% lower odds of use (OR = 0.99, [CI = 0.98,0.999]) and no difference in heavy use. In the adjusted models, years since MML enactment (OR = 0.93, [CI = 0.86,0.99]) and MML inclusion of more liberalized provisions (OR = 0.98, [CI = 0.96,0.998]) were associated with slightly lowered odds of past-30-day marijuana use. Conversely, allowance for ≥2.5 usable marijuana ounces was associated with higher past-30-day marijuana use odds (OR = 1.21, [CI = 1.09,1.34]) and a voluntary vs. mandatory patient registration with higher odds of both past-30-day use (OR = 1.41, [CI = 1.28,1.56]) and heavy use (OR = 1.23, [CI = 1.08,1.40]).ConclusionsMML enactment, years since enactment, and inclusion of more liberalized provisions were not associated with increased adolescent marijuana use in this dataset after adjusting for state and year effects; however, higher possession limits and a voluntary registration were. It is possible that state norms are the impetus for MML enactment.