More than two in five drivers – 42 % – who used alcohol and cannabis in the past year said they drove under the influence (DUI) of alcohol, cannabis or both, raising public health concerns. People who said they used alcohol and cannabis simultaneously were more likely to report driving under the influence of cannabis alone or combined with alcohol.
Those are the highlights of a new study of drivers with past year alcohol and cannabis use conducted by researchers at the Columbia University Mailman School of Public Health that examined whether simultaneous use of those substances is associated with higher odds of driving while intoxicated.
The findings, “Simultaneous Alcohol/Cannabis Use and Driving Under the Influence in the U.S.,” published in the American Journal of Preventive Medicine, were released on Tuesday.
“Alcohol and cannabis are two of the most common substances involved in impaired driving and motor vehicle crashes in the U.S.,” Priscila Dib Gonçalves in the Department of Epidemiology at Columbia Mailman School, and the paper’s lead author, said in a statement. “Examining the effect of simultaneous alcohol and cannabis use on self-report driving under the influence (DUI) of alcohol-only, cannabis-only, and both substances using a nationally representative sample could contribute to better understanding the impact in adolescents and adults.”
Research conducted previously suggested that simultaneous alcohol and cannabis use increases driving impairment, leading to an uptick in the risk of traffic fatality more than either substance individually, particularly among young adolescents, the study noted. But the researchers said that this was the first study of its kind to test the relationships between simultaneous use and driving under the influence of these substances.
“Our study is unique in that it reports more recent nationally representative data (2016-2019) and compares different types of DUI categories,” Gonçalves said.
The study sample included nearly 35,000 drivers who reported any past-year alcohol and cannabis use, specifically driving under the influence of alcohol-only (DUI-A), cannabis-only (DUI-C), alcohol and cannabis (DUI-A+C), or no DUI.
Between 2016-2019, 42% of drivers with past-year alcohol and cannabis use reported any past-year DUI (8% DUI-A, 20% DUI-C, 14% DUI-A+C). Simultaneous use was associated with 2.88 times higher odds of driving under the influence of cannabis, and 3.51 times higher odds of driving under the influence of both alcohol and cannabis.
Most participants were male (57%), non-Hispanic white (67%) with a family income of $40,000 or less (63%), and living in a state with medical cannabis laws (68%). Daily alcohol use was reported by 8%, daily cannabis use by 20%, and more than a quarter of the sample (28%) reported simultaneous alcohol/cannabis use.
Daily alcohol and cannabis use increased the likelihood of DUI-A and DUI-C, respectively, and both alcohol/cannabis daily use were associated with DUI-A/C.
“From a harm reduction perspective, identifying which population subgroups are at high risk for DUIs could assist the development of more focused prevention strategies,” Gonçalves added. “Future research should also investigate the potential impact of low or “promotional” cannabis prices with higher levels of use, intoxication, and simultaneous use of other substances.”