States with Legalized Medical Marijuana Have Higher Marijuana Use and Dependence: Using the Legalization of Medical Marijuana as a Proxy Measure of Community Norms

Magdalena Cerda, Columbia University
Melanie Wall, Columbia University
Katherine Keyes, Columbia University
Deborah Hasin, Columbia University

Marijuana use is the most frequently used illicit substance in the United States, and marijuana use disorder is the most common substance use disorder after nicotine and alcohol. We examined marijuana use and disorder rates by prior state-level legalization of medical marijuana. We considered state medical marijuana policy to reflect existing community norms on marijuana use. Our primary data source was the NESARC, a nationally-representative survey of adults aged 18+ (n=34,520). We replicated selected analyses using the NSDUH, an annual national survey of individuals aged 12+ (n=70,000). Accounting for potential individual- and state-level confounders, residents of states that had legalized medical marijuana had higher odds of past-year marijuana use (OR:1.89; 95% CI: 1.45,2.46) and marijuana use disorder (OR:1.79; 95% CI: 1.25,2.56) than residents of non-legalizing states. These findings highlight the impact that intervening on macro-level factors, such as social norms, may have in shaping the population distribution of marijuana use.