After Pennsylvania legalized medical marijuana in 2016, trauma centers saw a significant increase in motor vehicle crash victims testing positive for marijuana, with these patients being younger and having longer hospital stays.
Policy makers evaluating cannabis legalization impacts, public health researchers, emergency medicine professionals, and traffic safety advocates.
What the researchers found
Following medical marijuana legalization, marijuana positivity among MVC trauma patients increased significantly (p<0.0001), with marijuana-positive patients having longer hospital stays (+2 days) and higher rates of polysubstance use compared to marijuana-negative patients.
Why it matters
This large-scale real-world data from a single trauma center provides evidence that medical marijuana legalization correlates with increased marijuana-positive driving, informing road safety policy discussions.
The numbers in context
10,517 trauma patients; pre vs. post-legalization comparison over 16 years; marijuana-positive patients had +2 days longer hospital stays; significant increase in marijuana detection post-legalization (p<0.0001); higher polysubstance use (p<0.001)
How the study worked
Retrospective case-control study of 10,517 trauma patients from MVCs at a Pennsylvania trauma center from 2008-2024, comparing pre-legalization (2008-2016) and post-legalization (2016-2024) groups using Chi-square tests.
What this study cannot tell us
Single trauma center limits generalizability; correlation not causation; toxicology testing may have changed over the study period; positive test doesn't confirm impairment at time of crash; medical marijuana law may coincide with other policy changes.
How to read the evidence
Large sample retrospective study with clear pre/post comparison, but limited by single center, potential confounders, and inability to confirm impairment from positive test alone.
When this study was published
Published 2026; covers data through March 2024.
The bigger picture
As more states legalize cannabis, understanding its impact on traffic safety becomes critical — this study adds to evidence that legalization increases detection of cannabis among crash-involved drivers.
Questions still open
- Does recreational legalization show an even larger effect? Are the longer hospital stays due to marijuana itself or associated polysubstance use? How do impairment levels compare to alcohol-impaired drivers?
Common questions
Did marijuana-related car crashes increase after legalization?
Are marijuana-positive crash victims more severely injured?
Read the original research
Characteristics of trauma patients involved in motor vehicle collisions before and after legalization of medical marijuana in Pennsylvania.
The American journal of emergency medicine, 99, 296-300
Citation
Gimbel, Kirsten; Marco, Catherine A. (2026). Characteristics of trauma patients involved in motor vehicle collisions before and after legalization of medical marijuana in Pennsylvania.. The American journal of emergency medicine, 99, 296-300. https://doi.org/10.1016/j.ajem.2025.10.008