Marijuana use disorder is common in the United States, is often associated with other substance use disorders, behavioral problems, and disability, and goes largely untreated, according to a new study conducted by the National Institute on Alcohol Abuse and Alcoholism (NIAAA), part of the National Institutes of Health. The analysis found that 2.5 percent of adults - nearly 6 million people - experienced marijuana use disorder in the past year, while 6.3 percent had met the diagnostic criteria for the disorder at some point in their lives. A report of the study, led by Bridget Grant, Ph.D., of the NIAAA Laboratory of Epidemiology and Biometry, appears online today in the American Journal of Psychiatry.

"...Marijuana use can lead to harmful consequences for individuals and society."
- George F. Koob, Ph.D., Director, NIAAA

"The new analysis complements previous population-level studies by Dr. Grant's group that show that marijuana use can lead to harmful consequences for individuals and society," said George F. Koob, Ph.D., director of NIAAA.

In a recent report, Dr. Grant and her team found that 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 disorders during that time was nearly as large. The new study analyzed data about marijuana use that were collected in the 2012-2013 wave of NIAAA's National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), the largest study ever conducted on the co-occurrence of alcohol use, drug use, and related psychiatric conditions.

The researchers interviewed more than 36,000 U.S. adults about alcohol use, drug use, and related psychiatric conditions. Notably, the current study applies diagnostic criteria for marijuana use disorder from Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to the NESARC data. In DSM-5, marijuana dependence and abuse are combined into a single disorder. To be diagnosed with the disorder, individuals must meet at least two of 11 symptoms that assess craving, withdrawal, lack of control, and negative effects on personal and professional responsibilities. Severity of the disorder is rated as mild, moderate, or severe depending on the number of symptoms met.

Consistent with previous findings, the new data showed that marijuana use disorder is about twice as common among men than women, and that younger age groups are much more likely to experience the disorder than people age 45 and over. The risk for onset of the disorder was found to peak during late adolescence and among people in their early 20s, with remission occurring within 3 to 4 years. Also in keeping with previous findings, the new study found that past-year and lifetime marijuana use disorders were strongly and consistently associated with other substance use and mental health disorders.

Dr. Grant and her colleagues also reported that people with marijuana use disorder, particularly those with severe forms of the disorder, experience considerable mental disability. They note that previous studies have found that such disabilities persist even after remission of marijuana use disorder. The researchers also report that only about 7 percent of people with past-year marijuana use disorder receive any marijuana-specific treatment, compared with slightly less than 14 percent of people with lifetime marijuana use disorder.

"These findings demonstrate that people with marijuana use disorder are vulnerable to other mental health disorders," said Nora D. Volkow, M.D., director of NIDA, which contributed funding to the study. "The study emphasizes the need for such individuals to receive help through evidence-based treatments that address these co-occurring conditions."

The study authors note the urgency of identifying and implementing effective prevention and treatment for marijuana use disorder. And with ongoing changes in the drug's legal status at the state level and a shift in beliefs about the risks associated with its use, they also note that public education about the dangers associated with marijuana use will be increasingly important to address 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.

In June 2015, NIAAA published a study based on NESARC data showing that alcohol use disorder (AUD) was on the rise in the U.S. over the last decade. The results showed that nearly one-third of adults in the United States have an AUD at some time in their lives, but only about 20 percent seek AUD treatment.


Posted 3/6/16