Medical Marijuana Legalization and Marijuana Use Among Youth in Oregon

Legalization of marijuana for medical and recreational use raises concerns about possible influences that resulting increases in availability may have on adolescents’ marijuana use and beliefs. We examined the association between medical marijuana patients and licensed growers per 1,000 population in 32 Oregon counties from 2006 to 2015 and marijuana use among youth over the same period. Data on registered medical marijuana patients and licensed growers were obtained from the Oregon Medical Marijuana Program. Data on youth marijuana use, perceived parent disapproval, and demographic characteristics (age, gender, race/ethnicity) were obtained from the Oregon Healthy Teens Survey. Across counties, the mean rate of marijuana patients per 1,000 population increased from 2.9 in 2006 to 18.3 in 2015. Grower rates increased from 3.8 to 11.9. Results of multi-level analyses indicated there were significant positive associations between rates of marijuana patients and growers per 1,000 population and prevalence of past-30-day marijuana use among youth, controlling for individual demographic characteristics. The marijuana patient and grower rates were inversely associated with perceived parent disapproval of marijuana use, which decreased from 2006 to 2015. Including perceived parental disapproval in the models attenuated the relations between patient and grower rates and adolescents’ use. Changes in patient and grower rates across time were not associated with changes in the prevalence of marijuana use. These findings suggest that living in a county with more registered marijuana patients and growers is associated with a higher prevalence of marijuana use among youth, but this relationship is likely attributable to broader norms that are more favorable towards marijuana use.