UCSF

Introduction State legalization of marijuana for medical purposes could increase illicit marijuana use among young people. Medical marijuana laws may boost the availability of marijuana and reduce perceptions of its harmfulness, leading more young people to try it. Prior studies report little evidence that these laws are impacting marijuana consumption by young Americans, and none have systematically compared developmentally distinct age groups. Methods We performed multilevel, serial cross-sectional analyses on ten annual waves of U.S. National Survey on Drug Use and Health, from 2004 to 2013, comparing young people in states with and without medical marijuana laws. Disaggregated analyses compared multiple measures of marijuana use across approximately 450,300 individuals in early adolescence (12-14 years), late adolescence (15-17 years) and young adulthood (18-25 years). Results Dwelling in a state that had legalized medical marijuana was not associated with marijuana consumption in the past month among early adolescents, late adolescents or young adults. However, young adults living in medical marijuana states were significantly more likely to have initiated first use in the past year. Conclusions Medical marijuana laws increase the likelihood that young adults will start using marijuana but do not affect more vulnerable developmental groups in early and late adolescence. Delaying the age of first use into young adulthood can reduce the risk of a drug use disorder later in life. Young adults are in the peak years of engagement with illicit drugs and state medical marijuana laws appear to be leading larger numbers to try the drug.