More than 40% of drivers killed in motor vehicle crashes in one Ohio county tested positive for active THC, the psychoactive component of cannabis, according to a new study by the American College of Surgeons (ACS).
Researchers reviewed coroner records from Montgomery County between January 2019 and September 2024 and found that 41.9% of the 246 deceased drivers tested positive for THC, with an average blood level of 30.7 ng/mL. That’s several times higher than most state-defined impairment limits, which range from 2-5 ng/mL.
“An average level of 30.7 ng/mL generally means those people must have consumed marijuana at some time close to driving,” said lead author Dr. Akpofure P. Ekeh, a professor of surgery at Wright State University. “This isn’t about residual use; it’s about recent consumption.”
Legalization had no impact on usage rates
The researchers found that the legalization of recreational cannabis in Ohio in 2023 did not significantly alter THC positivity rates among deceased drivers. Before legalization, 42.1% of drivers tested positive for THC, compared with 45.2% afterward. The rate remained consistent throughout the 6-year study period.
“The messaging over the last few years has focused heavily on legalization,” Dr. Ekeh said. “The problem is that from a public health standpoint, there hasn’t been enough emphasis on the dangers. People should treat smoking marijuana just like they treat alcohol: don’t smoke and drive.”
Study underscores need for stronger education
The authors said the data highlights an ongoing need for public education about the risks of driving under the influence of cannabis. Because coroner blood samples are typically collected within hours of a crash, the study provides a reliable snapshot of THC presence at the time of the collision.
The research team — Lois Nguapa, BS; Clara Mussin Phillips, BS; and Ann Cardosi, BS, MPH — presented the findings in an abstract titled “Cannabis Prevalence in Drivers Involved in Motor Vehicle Crash Fatalities over a 6-Year Period.”
The study has been reviewed and accepted for presentation by the ACS Scientific Forum but has not yet undergone peer review.
