October 22, 2015

Study Finds the Prevalence of Marijuana Use Among U.S. Adults Doubled Over Past Decade

The percentage of Americans who reported using marijuana in the past year more than doubled between 2001-2002 and 2012-2013, and the increase in marijuana use disorder during that time was nearly as large. Past year marijuana use rose from 4.1 percent to 9.5 percent of the U.S. adult population, while the prevalence of marijuana use disorder rose from 1.5 percent to 2.9 percent, according to national surveys conducted by the National Institute on Alcohol Abuse and Alcoholism (NIAAA).

“Based on the results of our surveys, marijuana use in the United States has risen rapidly over the past decade, with about 3 in 10 people who use marijuana meeting the criteria for addiction. Given these increases, it is important that the scientific community convey information to the public about the potential harms,” said George Koob, Ph.D., director of NIAAA, in a news release.

Data about marijuana use was collected as part of NIAAA’s National Epidemiologic Survey on Alcohol and Related Conditions, a series of the largest epidemiological surveys of their kind. In total, 79,000 people were interviewed on alcohol use, drug use and related psychiatric conditions during the 2001-2002 and 2012-2013 surveys.

This analysis appears in this week’s issue of the Journal of the American Medical Association (JAMA) Psychiatry.

The marked increase in marijuana use and marijuana use disorder shown in the study is a significant change from prior results. Earlier NIAAA research found that marijuana use remained stable at about 4 percent of the U.S. population between 1991-1992 and 2001-2002, while abuse and dependence rose from 1.2 percent to 1.5 percent.

Based on the current study, approximately 30 percent of people who used marijuana in the past year met criteria for marijuana use disorder during 2012-2013, as defined by the Diagnostic and Statistical Manual of Mental Disorders. This includes symptoms such as taking the drug in larger amounts or over a longer period than was intended by the user; the persistent desire to cut down or control use/unsuccessful efforts to do so; failure to fulfill major role obligations at work, school or home as a result of marijuana use; and tolerance and/or withdrawal.

“These findings highlight the changing cultural norms related to marijuana use, which could bring additional public health challenges related to addiction, drugged driving and access to effective treatment,” said Nora D. Volkow, M.D., director of the National Institute on Drug Abuse (NIDA), which contributed funding to the study, also in a news release. “NIDA will continue to work with our partners at NIAAA and across the federal government to educate the public and policymakers on these and other issues related to the use of psychoactive drugs.”

The near doubling of the prevalence of marijuana use disorder among the U.S. population in the last decade can be attributed to the substantial increase in marijuana use overall, rather than an increase in rates of addiction among users. The proportion of users who have a marijuana use disorder was found to have actually decreased (35.6 percent to 30.6 percent) between 2001-2002 and 2012-2013. Symptoms of marijuana use disorder were assessed during face-to-face interviews.

When examined by age, young adults (ages 18 – 29) were found to be at highest risk for marijuana use and marijuana use disorder, with use increasing from 10.5 percent to 21.2 percent and disorder increasing from 4.4 percent to 7.5 percent over the past decade. Black and Hispanic individuals also showed especially noticeable increases in the prevalence of marijuana use and marijuana use disorder, with use increasing from 4.7 percent to 12.7 percent over the past decade among blacks and from 3.3 percent to 8.4 percent among Hispanics. The prevalence of marijuana use disorder increased from 1.8 percent to 4.6 percent among blacks and 1.2 percent to 2.8 percent among Hispanics over the same time period. All increases were found to be statistically significant.

Twenty-three states now have medical marijuana laws and four states, as well as the District of Columbia, have legalized marijuana for recreational use. Studies funded by NIDA and NIAAA have shown that marijuana impairs driving performance, increasing lane weaving, and that since the legalization of medical marijuana in Colorado, drivers involved in fatal motor vehicle crashes are significantly more likely to test positive for marijuana use. With changes in the drug’s legal status at the state level and a shift in beliefs about the risks associated with its use, the study authors note that public education about the dangers associated with marijuana use, presented in a reasonable and balanced manner, will be increasingly important to counteract public beliefs that marijuana use is harmless.

As marijuana and alcohol are frequently used together, more research is also needed to understand the effects of combined use. Studies suggest that using marijuana and alcohol together impairs driving more than either substance alone and that alcohol use may increase the absorption of THC, the psychoactive chemical found in marijuana.


CADCA’s Online Course: What Do We Know About Marijuana?

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