Adults who use marijuana are five times more likely to develop alcohol abuse or dependence compared with adults who do not use the drug. Adults who already have an alcohol use disorder and use marijuana are more likely to see the problem persist, finds a paper in Drug and Alcohol Dependence.

The researchers analyzed data from 27,461 adults enrolled in the National Epidemiologic Survey on Alcohol and Related Conditions who first used marijuana at a time when they had no lifetime history of alcohol use disorders. The population was assessed at two time points. Adults who had used marijuana at the first assessment and again over the following three years (23 percent) were five times more likely to develop an alcohol use problem, compared with those who had not used marijuana (5 percent).

Adult problem drinkers who did not use cannabis were significantly more likely to be in recovery from alcohol use disorders three years later.

"Our results suggest that cannabis use appears to be associated with an increased vulnerability to developing an alcohol use disorder, even among those without any history of this," said Renee Goodwin, PhD, associate professor of Epidemiology at Columbia University's Mailman School of Public Health. "Marijuana use also appears to increase the likelihood that an existing alcohol use disorder will continue over time.

"From a public health standpoint we recommend that further research be conducted to understand the pathways underlying these relationships as well as the degree to which various potentially vulnerable population subgroups -- youth, for example -- are at increased risk. If future research confirms these findings, investigating whether preventing or delaying first use of marijuana might reduce the risk of developing alcohol use disorders among some segments of the population may be worthwhile."