Characteristics of trauma patients involved in motor vehicle collisions before and after legalization of medical marijuana in Pennsylvania

Background: Marijuana is the most commonly used illicit drug in the U.S. Despite federal prohibition, state-level legalization has expanded. Pennsylvania legalized medical marijuana in 2016, prompting concerns about its impact on motor vehicle collisions (MVCs). Objectives: The goal of this study was to compare characteristics of trauma patients involved in MVCs before and after legalization of medical marijuana in Pennsylvania. Methods: We conducted a retrospective case-control study of trauma patients aged 18+ involved in MVCs at a Pennsylvania trauma center from March 2008 to March 2024. Patients were categorized into pre- (2008–2016) and post-legalization (2016–2024) groups. Data were obtained from the Pennsylvania Trauma Systems and included substance use, demographics, injury severity, and outcomes, and the data were analyzed using Chi-square tests and 95 % confidence intervals. Results: A total of 10,517 trauma patients presented following MVCs, with a significant rise in individuals driving under the influence of drugs or alcohol post-legalization of marijuana. Marijuana was the most frequently detected substance, with increased positivity post-legalization (p < 0.0001). Following legalization, motor vehicle crash victims were more often female, White, Hispanic or Latino, and discharged home (all p < 0.0001). In contrast, marijuana-positive patients were typically younger, male, non-White, and had longer hospital stays (+2 days) and higher rates of polysubstance use (all p < 0.001). Conclusion: Following the legalization of medical marijuana in Pennsylvania, there was an increase in motor vehicle crashes involving drivers who texted positive for marijuana, accompanied by a notable shift in the demographic profile of these drivers post-legalization. Marijuana use was associated with longer hospital stays and co-use of other substances, highlighting the need for ongoing surveillance and education on impaired driving risks.