The numbers from the morgue paint a stark picture that recreational cannabis laws apparently can’t change: More than 40% of drivers killed in car crashes in a major Ohio county had active THC coursing through their bloodstreams when they died, and the state’s 2023 move to legalize recreational marijuana didn’t budge that figure even slightly.

A six-year analysis of 246 deceased drivers in Montgomery County reveals a public health problem that researchers say has been overshadowed by the push toward legalization. Between January 2019 and September 2024, coroners consistently found THC-positive results in roughly four out of every ten fatal crash victims who were tested. The yearly rates bounced around (from a low of 25.7% to a high of 48.9%) but averaged 41.9% overall.

What makes the findings particularly concerning isn’t just the prevalence, but the potency. The average blood THC level among positive cases measured 30.7 nanograms per milliliter, a concentration that dwarfs the 2 to 5 ng/mL thresholds most states use to define impairment. At those levels, drivers weren’t dealing with residual traces from yesterday’s joint.

“An average level of 30.7 ng/mL generally means those people must have consumed marijuana at some time close to driving. This isn’t about residual use; it’s about recent consumption.”

That’s according to Dr. Akpofure P. Ekeh, a professor of surgery at Wright State University in Dayton, who led the research team. The findings will be presented at the American College of Surgeons Clinical Congress 2025 in Chicago this week.

Legalization Changed Nothing

Perhaps the study’s most provocative discovery is what didn’t happen. When Ohio legalized recreational cannabis in 2023, roughly halfway through the study period, the percentage of THC-positive deceased drivers barely moved: 42.1% before legalization versus 45.2% after. The legal shift that dominated headlines and sparked public debate apparently had zero impact on whether cannabis users decided to get behind the wheel while impaired.

The research relied on coroner records that included drug screening as part of standard autopsy procedures. Blood samples were typically drawn within hours of death, providing what researchers describe as an accurate snapshot of drivers’ conditions at the moment of their crashes. It’s data that exists precisely because these crashes were fatal, a selection bias that necessarily focuses on the most severe outcomes rather than the full spectrum of impaired driving incidents.

The consistency of the findings across six years suggests something deeper than statistical noise. Whether the rate hit 26% one year or 49% another, the underlying pattern remained: a substantial portion of people were using cannabis shortly before driving, with predictably deadly results.

The Messaging Gap

Dr. Ekeh argues the problem stems partly from an imbalance in public messaging. The cultural conversation around cannabis has tilted heavily toward normalization and legalization advocacy, while warnings about impaired driving have been drowned out.

“The messaging over the last few years has been just the push towards recreational legalization. The problem is that from a public health standpoint, there has not been enough emphasis on some of the downsides and the dangers that can occur.”

His prescription is straightforward: treat cannabis like alcohol when it comes to driving. Don’t smoke and drive. It’s not a revolutionary concept, but it’s one that clearly hasn’t penetrated as deeply as advocates might hope.

The study has limitations worth noting. It focuses on a single county in Ohio, and the research was presented as an abstract at a conference rather than published in a peer-reviewed journal. The data also can’t determine causation, whether THC directly caused these crashes or simply happened to be present in drivers who crashed for other reasons. And because the sample includes only deceased drivers, it can’t speak to the broader population of impaired drivers who survive their crashes or never crash at all.

Still, the findings add weight to growing concerns about cannabis-impaired driving at a moment when more states continue to liberalize their marijuana laws. The researchers suggest that legalization without robust public health messaging may be creating a dangerous void, one that’s being filled, quite literally, by bodies in the coroner’s office.

Co-authors of the study include Lois Nguapa, Clara Mussin Phillips, and Ann Cardosi.

Study Citation: Journal of the American College of Surgeons: 10.1097/01.XCS.0001062845.59348.00