Study: Marijuana and Alcohol Doubles Odds for DUI

Alcohol & Marijuana: A Dangerous Combination

Marijuana is becoming increasingly legalized in the US for medical and recreational use. A new study analyzes the simultaneous use of alcohol and marijuana. In short, simultaneous users had double the odds of drunk driving, social consequences, and harm to self and others.

The researchers analyzed data from the 2005 and 2010 National Alcohol Survey (n=8,626; 4,522 females, 4,104 males). This was a Random Digit Dial, Computer Assisted Telephone Interview survey of individuals aged 18 and older from all 50 states and DC. Blacks and Hispanics were over-sampled. The study authors assessed differences in demographics, alcohol-related social consequences, harms to self, and drunk driving across simultaneous, concurrent, and alcohol-only using groups.

“We looked at three groups of adults,” explained Meenakshi S. Subbaraman, a corresponding author for the study and associate scientist at the Alcohol Research Group, a program of the Public Health Institute. “One, those who used only alcohol in the previous 12 months; two, those who used both alcohol and cannabis but always separately, or concurrently; and three, those who used both alcohol and cannabis and usually together, or simultaneously.

According to the study, simultaneous users did not necessarily always use cannabis while they drank; the groups were based on how often they drank when using cannabis, and not vice versa.

The study authors found that, compared to adults who solely used alcohol, simultaneous users had double the odds of drunk driving, social consequences, and harms to self. Compared to concurrent users, simultaneous users had double the odds of drunk driving. Simultaneous users also had the heaviest drinking patterns in terms of quantity and frequency.

The research brought interesting conclusions. “If cannabis use becomes more prevalent as U.S. states and other countries continue to legalize it, then we need to be prepared to advise people appropriately,” cautioned Subbaraman. “If you use both substances together, your risk of drunk driving, and possibly other consequences, may be higher than if you stick to using one at a time.”

The study appears in the May 2015 online issue of the journal Alcoholism: Clinical & Experimental Research.