> How are they ruling out the fact that since it's been legalized, more people in general are using marijuana?

That's exactly the point. No one is trying to say that driving high has gotten more dangerous as a result of legalization - just that it's inherently dangerous (and a certain percentage of marijuana users are going to be driving either way), so legalization only contributes to more usage, leading to more irresponsible decisions on the road.

>Also, results of this study do not indicate that drivers with detectable THC in their blood at the time of the crash we re necessarily impaired by THC or that they were at-fault for the crash; the data availabl e cannot be used to assess whether a given driver was actually impaired, and examination of fault in individual crashes was beyond the scope of this study

If there was a general increase in accidents, I think you would have a point, but all this conclusively demonstrates is that there has been an increase of marijuana usage among the population of Washington. The thing about how these drug tests work, is that they do not test impairment or if someone was high at the time, but if they were high within the past few hours to days. I think you're misunderstanding, that even if there is THC in someone's bloodstream, it does not mean they are high. It is possible that none of the drivers in the study were high at the time of their crashes, and all of them smoked the day before. It is also possible that every single one was high during the collision. Due to the nature of the testing, the linked study is not very conclusive on at least what you're trying to prove from it.

My point is: They're getting this data by doing drug tests of drivers in fatal car crashes after the crash has occurred. Previously, 8% of those drivers had cannabis detected. Now, 17% have it detected.

What evidence is there that the increased cannabis use is causing these crashes, considering you have to control for the fact that more people in general are using cannabis, so in almost any population (drivers in fatal car crashes; fast food employees; school teachers; whatever) you could expect to see an increase in use.

Ah, I understand what you're saying now. Still, I think it'd be a stretch to assume that none of those fatalities were actually related to the marijuana use. But I agree, it doesn't necessarily imply causation, just a correlation (which as you say, could in part be coincidental).

It's a fine assumption. We could also assume that marijuana use discourages use while under the influence due to increased paranoia. Neither have been demonstrated yet.

All we know from this is that there was a increased detection of thc for people involved in fatal accidents. The reason for this seems obvious to me and I assume it correlates with general increased use among the population. I still conject that "fatal" accidents are used here to push a particular narrative. I don't see any significance in "fatal" versus cumulative accidents or DUI arrests.

If the intent is to prove that there is an increased hazard on the road due to marijuana use, then they need to prove that it's use significantly increases this hazard AND that the rate of drivers under influence has increased. Those are two separate and independent studies.

I'm still waiting to see those studies.

That's exactly what this particular study is trying to measure - whether there's a causative link. And they didn't find one (subject to the precision of their study, of course). Basically, yes, more people have higher blood levels, but this does not translate to more accidents.

You're right, it probably is a stretch. But since they have not demonstrated any evidence either way, the study basically has to be disregarded.

I doubt there is any. Else they would have quoted a cumulative increase in fatalities.