High THC Levels in Fatal Crashes: Study Reveals 40% of Drivers Tested Positive

High THC Levels in Fatal Crashes: Study Reveals 40% of Drivers Tested Positive

March 2, 2026 Ananya Mittal - World Editor News

Nearly half of drivers involved in fatal crashes in Montgomery County, Ohio, between 2019 and 2024 tested positive for the presence of delta-9-tetrahydrocannabinol (THC), the primary psychoactive component in cannabis. The finding, presented at the American College of Surgeons (ACS) Clinical Congress 2025, raises renewed concerns about the public health implications of cannabis use and driving safety, even as more states move toward legalization.

Consistent THC Detection Across Six Years

Researchers, led by Akpofure P. Ekeh, MBBS, FACS, a professor of surgery at Wright State University in Dayton, Ohio, reviewed coroner records from January 2019 through September 2024. The analysis encompassed 246 drivers who died in motor vehicle crashes and underwent toxicology screening as part of the standard autopsy process. The study revealed that 103 drivers (41.9%) had active THC in their systems at the time of death. Yearly rates of THC detection ranged from 25.7% to 48.9%, demonstrating a consistently high prevalence over the six-year period. Notably, the rate of THC positivity remained stable both before and after Ohio’s legalization of recreational cannabis in 2023 (42.1% vs. 45.2%).

“I was surprised to see that level,” Dr. Ekeh stated, emphasizing that the average THC level detected – 30.7 ng/mL – was significantly higher than the thresholds considered impairing in most states. As reported by news sources, this suggests recent cannabis consumption rather than residual presence from past use.

Understanding THC Levels and Impairment

Determining impairment from THC is complex. Unlike alcohol, where blood alcohol content (BAC) provides a relatively clear indicator of intoxication, the relationship between THC levels and driving ability is less straightforward. Leafie.co.uk highlights that THC levels can vary widely depending on factors such as frequency of use, method of consumption, and individual metabolism. Most states with legal limits for driving set the threshold at between 2 and 5 nanograms per milliliter (ng/mL). The average level found in this study – 30.7 ng/mL – far exceeds these limits, indicating a substantial degree of recent THC exposure among drivers involved in fatal crashes.

It’s important to note that this study, presented at the ACS Clinical Congress Scientific Forum, involved research abstracts that have not yet undergone full peer review. While the findings are concerning, further research is needed to confirm these results and explore the underlying factors contributing to the high prevalence of THC in drivers involved in fatal crashes.

The Broader Context of Cannabis and Traffic Safety

The findings from Montgomery County align with a growing body of evidence suggesting a link between cannabis use and impaired driving. ScienceDaily reports that nearly half of drivers killed in crashes have THC in their blood. This is a significant public health concern, particularly as more states legalize cannabis for recreational or medical use. The study’s finding that legalization did not significantly alter the rate of THC-positive drivers suggests that simply changing the legal status of cannabis does not necessarily translate to safer roads.

Challenges in Establishing Causation

While the correlation between THC and fatal crashes is evident, establishing a direct causal link remains challenging. Many crashes involve multiple factors, including alcohol, speeding, distracted driving, and other substances. It can be tough to isolate the specific contribution of THC to a crash, particularly given the complexities of measuring impairment and the potential for interactions between different substances. The study relies on postmortem toxicology data, which provides a snapshot of a driver’s state at the time of death but does not capture the full circumstances leading up to the crash.

Public Health Implications and Future Directions

The researchers emphasize the need for stronger and clearer public messaging about the risks of driving under the influence of cannabis. Dr. Ekeh advocates for treating cannabis use with the same caution as alcohol consumption: “People should treat smoking marijuana just like they treat alcohol: don’t smoke and drive.” This message is particularly crucial in light of the increasing normalization of cannabis use and the potential for individuals to underestimate the impairing effects of THC.

Moving forward, several steps are needed to address this growing public health concern. These include:

  • Enhanced law enforcement efforts to detect and deter impaired driving, including improved training for officers in recognizing the signs of cannabis impairment.
  • Development of more reliable and accurate methods for measuring THC impairment, such as roadside testing devices.
  • Continued research to better understand the effects of cannabis on driving ability and the factors that contribute to crashes.
  • Comprehensive public education campaigns to raise awareness about the risks of driving under the influence of cannabis.

The study’s authors suggest that further investigation is warranted to explore the potential impact of different cannabis products (e.g., edibles vs. Smoked cannabis) on driving impairment. Research is needed to assess the effectiveness of various interventions aimed at reducing cannabis-impaired driving.

What comes next: The American College of Surgeons will continue to monitor research in this area and update its clinical guidelines as recent evidence emerges. State and local authorities are similarly likely to review their policies and regulations regarding cannabis and driving safety in light of these findings. Ongoing surveillance of THC levels in drivers involved in crashes will be essential to track trends and assess the effectiveness of prevention efforts.