Some helpful context: The number of Americans age 12 and older who report using any marijuana product at least once in the past year is around 20% (Source https://apnews.com/article/marijuana-cannabis-alcohol-use-di... ) if I use one of the highest reported use numbers I can find.

Even if you dismiss all of the questions brought up in these comments like the use of mean levels instead of median, not accounting for tolerance of habitual users, or debates about the threshold for impairment, the 40% number in this study is without a doubt far higher than the number of people who have detectable levels of THC in their blood at any given time.

I see a lot of attempts to downplay the result of this study in the comments, but 40% having significant THC in their blood is a stunning statistic no matter how you look at it.

The biggest problem with drawing conclusions from the 40% number is that THC use correlates with other well established crash death risks like being a young driver or the use of other impairing substances.

The fact that legalization did not impact the crash rates is also a strong signal that THC itself is not causing the crashes.

The presence of THC in the blood is not a reliable signal for intoxication, so further research is needed to draw any type of conclusion.

Finally, it's also been noted that there are some sample bias concerns because the data comes from fatal crashes where it was determined that a drug test should be administered after the crash.

No not at all. Let's do it this way:

What percentage of people who drive drunk have consumed thc within the time window of blood detection?

Now this is a more reasonable number

I really don't know why this number is significant. Accidents are situational and people who engage in situations where accidents are more frequent likely make other decisions about consumption and lifestyle which involve things like cannabis

Who cares?

You aren't going to elevate the behavior of the population by regulating a plant

> 40% having significant THC in their blood is a stunning statistic no matter how you look at it.

Yes, it is a stunning statistic.

So much so, that in itself it makes it worth questioning the results of this study.

If 40% of fatal crash victims had THC in their bloodstream, and only 20% of the general population did, that would imply a 100% increase in chances of dying in a car crash from having smoked marijuana. That's an absolutely massive risk factor, the kind you would expect to show up very, very clearly in any kind of statistical analysis of car crashes.

But the other thing I've seen a bunch of people cite in this discussion is that there has been no statistically significant increase in fatal crashes following marijuana legalization.

That would imply that either there was no statistically significant increase in drivers high on marijuana since legalization, or there was no statistically significant increase in the likelihood of causing a fatal crash from being high on marijuana.

Based on our knowledge of human nature, the former seems incredibly unlikely (yes, there would surely be some people who would have been smoking pot before who just stopped hiding it as much, but there would also, just as surely, be many people who had been interested in getting high before, but who had been intimidated by its legal status or had no idea how to find a dealer until there were dispensaries opening in every town).

The latter directly contradicts the implication of this study—but this is only one study, and may have methodological issues that we are unaware of.

The number of people who report using it is only a rough proxy for the number of people who are using it, though.

You can't drive at 12 though surely? And you have to account for the fact that young people are going to be more likely to die in crashes and more likely to use weed.

This kind of test seems silly. It's going to be far too hard to remove the confounding variables. Much easier just to give people different levels of weed and have them do driving tests. Directly measure their driving skill instead of doing it by shitty proxy like this.

Surely this has been done?

You really think there arnt 20% of people who use but don’t report? What a crock of shit.

The n for the group is only 246 though. That’s very biased depending on where the stats are from.