Using Marijuana and Drinking at the same time Increases Risky Behavior Such as Impaired Driving, Study Says

A new study examined the relationship between marijuana and alcohol use, finding that simultaneous users had double the odds of participating in high-risk behavior such as impaired driving, social consequences and harm to self.

Results will be published in the May 2015 online-only issue of Alcoholism: Clinical & Experimental Research.

"There has been some disagreement regarding whether using cannabis and alcohol together is more dangerous than using either alone," said Meenakshi S. Subbaraman, corresponding author for the study and associate scientist at the Alcohol Research Group, a program of the Public Health Institute, in a news release. "My study is the first to compare how simultaneous and concurrent use of alcohol and cannabis relate to drunk driving and other social consequences among adults, and the first to examine differences between simultaneous and concurrent users in terms of demographics and substance use quantity/frequency. In this study, concurrent means having used both alcohol and cannabis within the previous 12 months, but always separately."

Researchers analyzed data from the 2005 and 2010 National Alcohol Survey, conducted telephonically. The study authors assessed differences in demographics, alcohol-related social consequences, harms to self, and impaired driving across simultaneous, concurrent, and alcohol-only using groups.

The study authors found that, compared to adults who solely used alcohol, simultaneous users had double the odds of impaired driving, social consequences, and harms to self. Compared to concurrent users, simultaneous users also had double the odds of impaired driving and were more likely to engage in high-risk drinking.

Center director Tom Greenfield noted that the timing of the study couldn’t be better.

“Because of both the number of states permitting medical marijuana, and differing legalizations…as well as efforts in other states for legalization, this is a timely study and indeed it is an understudied issue,” he said in a news release.

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