Background and Aims: Connections between substance use, impairment, and road safety have been frequently researched. Yet, little is known about how simultaneous use of opioids and alcohol affects road safety outcomes, which is an increasingly critical link to improve health outcomes for people with alcohol, opioid, or heroin use disorders as well as reduce wider driving-related risk for the general public. Given the increasing rate of opioid use and high prevalence of alcohol use, we aim to synthesize literature on the prevalence and impact of this polysubstance combination on road safety-related outcomes.
Methods: We performed a systematic review of studies published between 1974 and 2020 that examined opioid and alcohol use exposures and road safety-related outcomes.
Results: Twenty studies were identified. Studies utilized randomized control trial (n=2), cross-sectional (n=15), and case-control designs (n=3) and were of moderate methodological quality. Outcomes included motor vehicle crash injuries, deaths, or driver culpability; suspected driving under the influence; and simulated driving performance. There was a dearth of studies that isolated findings for simultaneous opioid and alcohol use, making the ability to draw strong conclusions on their relationship challenging, and presenting an opportunity for further research. Per available results, evidence pointed to elevated risks in road safety outcomes for simultaneous use of opioids and alcohol, compared to when neither or only one substance was present.
Conclusions: Research indicates that alcohol and opioid use is common and increasing among people involved in adverse driving events and that simultaneous use may further elevate risk. Future research can improve estimates of associations with road traffic-related outcomes, potentially using linked data sets or other novel data sources.