Study Explores Simultaneous Use of Substances on Impaired Driving Impact

Two in five drivers reporting alcohol and cannabis use in the past year said they drove under the influence (DUI) of alcohol, cannabis or both, according to a recent study from Columbia University Mailman School of Public Health.

The study is unique in that it reports more recent nationally representative data (2016-2019) and compares different types of DUI categories.

Specifically, between 2016-2019, 42% of drivers with past-year alcohol and cannabis use reported any and all past-year DUIs (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.

This study is unique in that while earlier research has 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, there was no hard evidence. Until now, no nationally representative study has tested relationships simultaneous use and people reporting driving under the influence of these substances.

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. 

Every day, approximately 28 people in the U.S. die in drunk driving crashes — that’s one person every 52 minutes. In 2019 alone, 10,142 people lost their lives to drunk driving. Moreover, some 56% of drivers involved in serious injury and fatal crashes tested positive for at least one drug, according to the National Highway Traffic Safety Administration (NHTSA).