Marijuana use in the United States more than doubled over the period from 2001-2002 to 2012-2013, while the increase in disorders associated with marijuana use was almost as large for that period.

Deborah Hasin, PhD, professor of clinical epidemiology at the Mailman School of Public Health and Columbia University Medical Center, and colleagues found that nearly 3 out of 10 marijuana users experienced a marijuana use disorder of abuse or dependence in 2012-13, affecting some 6,846,000 Americans. Findings are published online in JAMA Psychiatry.

Across the U.S., laws and attitudes towards marijuana are becoming more permissive, but there has been little investigation into whether marijuana use and marijuana use disorders are on the rise. To address this, the authors compared data from two U.S. national surveys, one of 43,093 individuals conducted in 2001-2002, and the other of 36,309 individuals, conducted in 2012-2013. Very similar measures and procedures were used in the two surveys, allowing for comparisons.

Results showed that the prevalence of using marijuana in the previous 12 months was more than twice as high in 2012-2013 (9.5%) compared to 2001-2002 (4.1%), a significant increase. Marijuana use disorders also increased substantially, from 1.5% of the adult population in 2001-2002 to 2.8% in 2012-2013. The rise in marijuana use disorders was attributed to the increase in the prevalence of marijuana users.

These findings were generally consistent across age, sex, race/ethnicity, education, income, urban/rural and region of the U.S. The results were also consistent with other studies showing increases in problems associated with cannabis, for example, cannabis-related emergency room visits and fatal car crashes, and indicate that as the prevalence of U.S. marijuana users increases, so will the number of individuals at risk for cannabis-related problems.

“At a time when Americans increasingly view marijuana use as harmless and favor its legalization, our findings suggest the need for caution and more public education about the potential for harms is warranted,” said Dr. Hasin. “This information is important to convey in a balanced manner to health professionals, policy makers and the public as the U.S. continues to consider legalization.”