Cannabis use disorder--or problematic use--among adults increased after legalization of recreational marijuana use, according to a new study from Columbia University Mailman School of Public Health and NYU School of Medicine. Among adults aged 26 or older, past-month marijuana use after legalization was 26 percent higher than in non-recreational states. Similarly, frequent use rose by 23 percent, and cannabis use disorder increased by 37 percent in these legal states. Similarly, there was a small increase in cannabis use disorder in youth in these states. The study is the first to look at the impact of recreational marijuana legalization on both use and cannabis use disorder across multiple age groups. Findings are published online in JAMA Psychiatry.
Presently, 11 states and Washington, D.C. have legalized marijuana for recreational use while 33 states and D.C. have legalized marijuana for medical use.
"Research has shown that cannabis use disorder can be associated with long-term adverse health, economic and social consequences," said Silvia S. Martins, MD, PhD, Associate Professor of Epidemiology at Columbia University Mailman School of Public Health, Director, Center on Policy and Health Initiatives on Opioids and Other Substances (PHIOS), and the study's senior author. "Given our findings on frequent and problematic use across age groups, legalization efforts should happen in tandem with funding for prevention and treatment. The general public should be informed about both benefits and potential harms of marijuana products to make informed decisions."
The researchers analyzed data from the National Survey on Drug Use and Health (NSDUH) with a sample of 505,796 respondents. They specifically looked at data from Colorado, Washington, Alaska, and Oregon from 2008-2016, the first four states to legalize marijuana for recreational use, and compared trends in these states to trends in states that had not legalized recreational marijuana use. The team also examined marijuana use and frequent use (more than 20 days) in the past month, and cannabis use disorder over the past year. Respondents were classified as having cannabis use disorder based on symptoms corresponding to DSM-IV criteria.
After examining usage following the enactment of marijuana legalization in 2012 to 2015, the researchers also report:
- Problematic use among adolescents aged 12 to 17- there was a small increase from 2.18 to 2.72 percent comparing the period after versus before legalization. There was no change in the prevalence of past-month or frequent use among teens.
- Among young adults aged 18 to 25, there was no difference found in past-month, frequent or problematic marijuana use.
"There are, indeed, important social benefits that legalizing marijuana can provide, particularly around issues of equity in criminal justice," said Magdalena Cerdá, DrPH, Associate Professor and Director of the Center for Opioid Epidemiology and Policy in the Department of Population Health at NYU Langone Health, and the study's lead author. "Our findings suggest that as more states move toward legalizing marijuana for recreational use, we also need to think about investing in substance use prevention and treatment to prevent unintended harms--particularly among adolescents."
Other factors besides legalization could also explain the small rise in the risk of cannabis use disorder among adolescents, noted the investigators, and will require further study.
Co-authors include Christine Mauro, Ava Hamilton, Natalie S. Levy, Julian Santaella-Tenorio, Deborah Hasin, Melanie M. Wall, and Katherine M. Keyes, of Columbia Mailman School.
Funding for the study was provided by the National Institute on Drug Abuse grant (DA037866).