Correct knowledge of medical cannabis legal status in one's own state: Differences between adolescents and adults in the United States, 2004–2013

Background: Studies have found age-specific effects of medical cannabis laws (MCLs), particularly affecting adult cannabis use but not adolescent use. We examined whether age differences in MCL knowledge are in accordance with age differences in MCL effects on cannabis use. Methods: Data from the 2004–2013 repeated cross-sectional National Surveys on Drug Use and Health included people ages 12 and older in the United States. State-aggregated MCL knowledge was the proportion of people that correctly identified living in a state that did not allow medical cannabis prior to MCL enactment, or that allowed medical cannabis after MCL enactment. We regressed state-aggregated MCL knowledge on time-varying MCL enactment (i.e., no MCL by 2015, before MCL, after MCL), testing associations by age strata (12–17, 18–25, 26+), open dispensary status, and adjusting for time and state-level demographics. Results: Model-based MCL knowledge was significantly lower among adolescents than adults; after enactment, 36.8% of ages 12–17, 48.8% of ages 18–25, and 45.4% of ages 26+ were aware of their state's MCL status. Correct MCL status knowledge decreased across all age groups after MCL enactment (i.e., low knowledge of MCL changes at the time they occurred). Open cannabis dispensaries significantly increased correct MCL knowledge, with a 7.7-point increase for adolescents and a 17.5-point increase for adults 26 +. Conclusions: Lower MCL knowledge among adolescents than adults was in accordance with MCL effects on cannabis use previously observed among adults only. Studies should assess whether MCL knowledge is a consequence or predictor of individual-level cannabis use across age groups.