http://www.drugfree.org/join-together/community-related/study-finds-teen-drug-use-not-affected-by-state-medical-marijuana-law

The study of almost 33,000 students compared trends in teenage marijuana use in Rhode Island and Massachusetts from 1997 to 2009, HealthDay reports. The researchers found between 26 and 34 percent of teenagers in both states used marijuana during that period, but there was no significant difference in marijuana use between the states in any year. They concluded Rhode Island’s law did not lead to increased marijuana use.