Cannabis use disorder: The policy climate matters

"The majority of existing work has explored the relationship between medical cannabis laws and cannabis outcomes, whereas our results identified important relationships between the state-level policy context as a whole, and cannabis use outcomes," said Morgan Philbin, PhD, assistant professor of Sociomedical Sciences, and first author. "While this research does not suggest that being in a liberal state causes people to use cannabis, or have lower rates of cannabis use disorder, it does highlight how states may differ beyond substance use policies, and how these differences also merit attention."

Using nationally-representative state-level data, the researchers examined the associations between policy liberalism and cannabis use and cannabis use disorder among past year users. Data were obtained for ages 12-17, 18-25, and 26 and older from the 2004-2006 and 2010-2012 National Survey on Drug Use and Health.

Past year cannabis use was consistently higher in liberal compared to conservative states, and remained significantly higher for ages 12-17 and 18-25 after adjusting for medical cannabis law status. As of December 2018, a total of 33 states had approved medical cannabis laws and eight states plus Washington, D.C. had legalized cannabis use.

Prevalence of cannabis use has increased overall since 2007 which has raised concerns about potential negative consequences associated with problematic use, specifically cannabis use disorder. "These latest findings could directly inform policymakers and public health practitioners about the degree to which other broader contextual factors also influence cannabis use patterns in the U.S.," noted Philbin.

States were categorized as liberal, moderate, or conservative based on the 2005 and 2011 State Rank on Policy Liberalism Index, which is based on policy indicators for which liberals and conservatives commonly differ. The Index ranked each state from 1 (most liberal) to 50 (most conservative) based on its policies regulating gun control, abortion access, Temporary Assistance to Needy families, collective bargaining, and tax structure.

Average state-level prevalence of past-year cannabis use by age was lowest for ages 26 and older and highest for ages 18 to 25 throughout the study period. Average prevalence increased for ages 18-25 in liberal states, from 33 percent to 37 percent, and rose marginally in conservative states, from 25 percent to 26 percent. The same pattern of use was observed for ages 26 and over in liberal (8 percent to 10 percent) and conservative (6 percent to 7 percent) states. For ages 12-17, however, past year use did not significantly change from 2004-2006 to 2010-2012 in liberal or conservative states.

In contrast, cannabis use disorder among past-year cannabis users decreased from 2004-2006 to 2010-2012 among those aged 18-25 in conservative states (22 percent to 18 percent) and liberal states (20 percent to 17 percent). Among individuals ages 26 and over, cannabis use disorder among past-year users decreased in liberal states (11 percent to 8 percent). For 12-17 year olds, cannabis use disorder decreased in conservative states (28 percent to 25 percent), though still remained marginally higher than in liberal states (24 percent).

"Our study highlights the need for researchers and public health professionals to distinguish between cannabis use and cannabis use disorder when interacting with patients at the individual level and when developing primary prevention strategies and interventions at the population level," said Silvia Martins, MD, PhD, associate professor of Epidemiology and senior author. "This line of research not only helps identify how state-level policies as a whole impact cannabis use outcomes, but ultimately supports the development of more health-promoting policies."

The work was funded by the National Institutes of Health/National Institute on Drug Abuse (DA037866, DA039804A, DA031099).

Co-authors are Pia Mauro, Julian Santaella-Tenorio, Christine Mauro, and Elizabeth Kinnard, Columbia Mailman School; and Magdalena Cerdá, New York University.