[Editor's note: This post is excerpted from this week's forthcoming NORML weekly media advisory. To have NORML's news alerts and legislative advisories delivered straight to your in-box, sign up here.]

The legalization of cannabis for therapeutic purposes is not associated with increases in the use of marijuana or other illicit substances among adolescents, according to discussion paper commissioned by the Institute for the Study of Labor (IZA) in Germany.

Economists from Montana State University, the University of Oregon, and the University of Colorado, Denver examined the relationship between state medical cannabis laws and marijuana consumption among high school students. Authors analyzed data from the national and state Youth Risky Behavior Surveys (YRBS) for the years 1993 through 2009 – during which time 13 states enacted law allowing for the production and use of cannabis for medicinal purposes.

The national YRBS is conducted biennially by the Centers for Disease Control and Prevention (CDC) and is a nationally representative sample of U.S. high school students.

Authors reported that the survey data provides no evidence that the enactment of medical cannabis legalization adversely impacted adolescents’ drug consumption. They concluded: “Our results are not consistent with the hypothesis that the legalization of medical marijuana caused an increase in the use of marijuana and other substances among high school students. … Our results suggest that the legalization of medical marijuana was not accompanied by increases in the use of marijuana or other substances such as alcohol and cocaine among high school students. Interestingly, several of our estimates suggest that marijuana use actually declined with the passage of medical marijuana laws.”

A 2012 study by researchers at McGill University in Montreal and published in the journal Annals of Epidemiology previously reported similar findings, concluding: “[P]assing MMLs (medical marijuana laws) decreased past-month use among adolescents … and had no discernible effect on the perceived riskiness of monthly use. … [These] estimates suggest that reported adolescent marijuana use may actually decrease following the passing of medical marijuana laws.”

Previous investigations by research teams at Brown University in 2011 and Texas A&M in 2007 made similar determinations, concluding, “[C]onsistent with other studies of the liberalization of cannabis laws, medical cannabis laws do not appear to increase use of the drug.”

The findings of these studies contradict public statements made by Drug Czar Gil Kerlikowske and other medical cannabis opponents, who in recent years have repeatedly alleged that the passage of medical cannabis laws is directly responsible for higher levels of self-reported marijuana consumption among US teenagers.

Full text of the study, “Medical Marijuana Laws and Teen Marijuana Use,” is available online at: http://ftp.iza.org/dp6592.pdf.