Marijuana Policy Project

The Impact of State Medical Marijuana Laws

The debate over medical marijuana laws has included extensive discussion of whether such laws “send the wrong message to young people” and increase teen marijuana use. This is an updated version of the first report that analyzed all available data to determine the trends in teen marijuana use in states that have passed medical marijuana laws.

Nearly 15 years after the passage of the nation’s first state medical marijuana law, California’s Prop. 215, a considerable body of data shows that teens’ marijuana use has generally gone down following the passage of medical marijuana laws. Of the 13 states with effective medical marijuana laws with before-and-after data on teen marijuana use, only the two with the most recently enacted laws (Michigan and New Mexico) have indicated possible increases, both of which are modest and within confidence intervals. In Rhode Island, the data indicate teens’ lifetime marijuana may have slightly decreased while current use may have slightly increased, but those changes are also within confidence intervals. The 10 remaining states have all reported overall decreases — some of which are also within confidence intervals and some of which are significant. Generally, no state with an overall change outside of the confidence intervals saw an increase in teens’ marijuana use, strongly suggesting that enactment of state medical marijuana laws does not increase teen marijuana use.