Between 1996 and 2011, 16 states passed laws legalizing use of marijuana for medical purposes when medically authorized [1]. Due to the potential for serious short- and long-term consequences of marijuana use in adolescence [2–7], prevention of adolescent marijuana initiation is a key NIDA strategy [8]. Although the potential impact of MML has been much discussed in the popular press, formal scientific assessments of the relation between MML and adolescent marijuana use using national data are lacking. Using 2002–2008 data from the National Survey on Drug Use and Health (NSDUH), we compared the prevalence of marijuana use and perceptions of its riskiness among 12–17 year olds in states that have passed medical marijuana laws (MML) to states without such laws.
