The Effects of Marijuana Liberalizations: Evidence from Monitoring the Future

By the end of 2016, 28 states had liberalized their marijuana laws: by decriminalizing possession, by legalizing for medical purposes, or by legalizing more broadly. More states are considering such policy changes even while supporters and opponents continue to debate their impacts. Yet evidence on these liberalizations remains scarce, in part due to data limitations.
We use data from Monitoring the Future’s annual surveys of high school seniors to evaluate the impact of marijuana liberalizations on marijuana use, other substance use, alcohol consumption, attitudes surrounding substance use, youth health outcomes, crime rates, and traffic accidents. These data have several advantages over those used in prior analyses.
We find that marijuana liberalizations have had minimal impact on the examined outcomes. Notably, many of the outcomes predicted by critics of liberalizations, such as increases in youth drug use and youth criminal behavior, have failed to materialize in the wake of marijuana liberalizations.