Despite these concerns, several studies have failed to find a measurable effect of legalization for medical use on adolescent prevalence using a pre–post analysis (43), a comparison with regionally proximate states (42), or a difference-in-differences analysis (52). Two of these studies, however, did not include data from marijuana-policy bellwether states such as Colorado, California, or Washington (42, 52). Data from the Youth Risk Behavior Survey (sponsored by the Centers for Disease Control and Prevention) show an increase in youth rates of marijuana use (from 2011 to 2013) in New Mexico since medical marijuana was legalized in 2009, although this trend among adolescents has thus far not been found in other states (53).
