The enactment of state laws legalizing the use and distribution of cannabis for medical purposes has not caused an increase in marijuana use by adolescents, according to the results of a federally funded study published this week in Lancet Psychiatry.
Investigators at Columbia University in New York and the University of Michigan assessed the relationship between state medical marijuana laws and rates of self-reported adolescent marijuana use over a 24-year period in a sampling of over one million adolescents in 48 states. Researchers reported no increase in teens’ overall use of the plant that could be attributable to changes in law, and acknowledged a “robust” decrease in use among 8th graders.
They concluded: “[T]he results of this study showed no evidence for an increase in adolescent marijuana use after the passage of state laws permitting use of marijuana for medical purposes. … [C]oncerns that increased marijuana use is an unintended effect of state marijuana laws seem unfounded.”
The study’s results are consistent with the findings of previous assessments — such as those available here, here, here, here, and here. But this latest study is the most well designed and comprehensive assessment performed to date.
Full text of the study, “Medical marijuana laws and adolescent marijuana use in the USA from 1991 to 2014: results from annual, repeated cross-sectional surveys,” appears online here.