> In a review of 246 deceased drivers, 41.9% tested positive for active THC in their blood, with an average level of 30.7 ng/mL — far exceeding most state impairment limits.

That could mean they all had levels far exceeding most state impairment limits, but it also could mean most of them had trace levels, while a few had levels way above 30.7 ng/mL. So, it says fairly little.

Also (FTA) “Researchers analyzed coroner records from Montgomery County in Ohio from January 2019 to September 2024, focusing on 246 deceased drivers who were tested for THC following a fatal crash”. That means there could be selection bias at play.

Finally, no mention is made on the levels of THC in the general population of of those driving cars. Both _could_ be equal or even higher.

I’m not sure one should blame (only) the researchers for these statements, though. Chances are they didn’t intend to find out whether THC use is a major cause of vehicle crashes, but only in whether legalizing THC use changed those numbers, and someone managed to get some more juicy quotes from them.

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notatoad a day ago | parent | next [-]

>focusing on 246 deceased drivers who were tested for THC following a fatal crash”. That means there could be selection bias at play.

that wording definitely sets off warning alarms for selection bias. but it looks like there were approximately 350 traffic deaths in montgomery county during that period [1]. that probably about lines up with 246 drivers dying during that period, so it seems likely they tested all or almost all deceased drivers.

[1] https://dam.assets.ohio.gov/image/upload/statepatrol.ohio.go...

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themafia a day ago | parent | prev | next [-]

They failed to present the average _age_ of the drivers as well. Young drivers are more often involved in fatalities than older drivers. This is clear if you look at the NHTSA's FARS database.

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thrill a day ago | parent | prev | next [-]

“Finally, no mention is made on the levels of THC in the general population of those driving cars.”

How do you propose gathering that particular data?

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Aurornis a day ago | parent [-]

One helpful data point is that only about 20% of people over age 12 report any THC use at all in the prior year. Some surveys have even lower numbers, around 1 in 8, but let’s take the highest number for the sake of this comparison.

So the median THC level is 0%.

Having 40% of people register high enough levels of THC to pass an impairment threshold is a remarkably high number no matter how you look at it.

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VanTheBrand a day ago | parent [-]

I think there is definable a connection between cannabis use and auto accidents. It slows your reaction time and that’s a known factor with accidents. That said, substance use data is notoriously underreported[1] in surveys. So that 20% data point is not very helpful. Also 12-15 year olds are bringing that number down in your data and also can’t drive making it even less useful for comparison.

[1]https://www.sciencedirect.com/science/article/pii/S089085672...

	▲	LorenPechtel a day ago \| parent [-]
		And substance use impairment is overreported. If the driver was impaired it's counted even if the impairment has no bearing on the accident. A drunk hits a red light runner--it's called alcohol even if he had no hope of avoiding it. My understanding of stoned drivers is they tend to be too conservative--waiting for the stop sign to turn green etc. If that's accurate it could also mean stoned drivers are worse at avoiding the mistakes of others.

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flufluflufluffy a day ago | parent | prev [-]

Came here to say most of this, also worth calling out the note at the bottom:

> Note: This research was presented as an abstract at the ACS Clinical Congress Scientific Forum. Research abstracts presented at the ACS Clinical Congress Scientific Forum are reviewed and selected by a program committee but are not yet peer reviewed.

My guess is when it gets to peer review, one of the reviewers will request at least mentioning these limitations. As it was only an abstract, it’s possible the paper itself does mention these limitations already as well.

	▲	lokar a day ago \| parent [-]
		They must have access to the full data distribution, right?