Auto Accidents Linked to Cannabis Use Increases with Legalization, Study Finds

Researchers from Canada say new impaired driving laws are needed to protect public safety in that country, as U.S. regulators face similar problems linked to rising use of cannabis and legalized marijuana throughout the United States

The findings of a new study highlights the growing problem of injuries caused by auto accidents involving cannabis use, which appears to increase with widening legalization of marijuana.

Researchers from Canada published a report this month in the Journal of American Medical Association (JAMA), indicating that the annual rate of car accident injuries related to cannabis use has increased nearly fivefold since 2010.

The study comes five years after Canada began legalizing the use of cannabis products nationally in stages. However, researchers warn that as cannabis use increased, so did the number of severe injuries linked to impaired driving auto accidents, leading to calls for new laws aimed at keeping marijuana-impaired drivers from behind the wheel.

The findings also pose concerns for U.S. safety officials, after at least 23 states passed measures in recent years legalizing recreational use of marijuana and more than a dozen others have legalized medical cannabis.

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In this latest study, researchers analyzed data on about 947,604 traffic injuries involving cannabis use. They looked at several specific periods of time; from the pre-legalization period of January 2010 through September 2018, the period of legalization with restrictions from October 2018 through February 2020, and the period after legalization without restrictions, from March 2020 until December 2021.

According to the findings, the number of auto accident injuries related to cannabis use has increased 475.3% from 2010 until the end of 2021. The data indicates there was an increase of 94% in the period just before marijuana was legalized, followed by an increase of 223% in cannabis-related car accident injuries after full legalization.

Following the unrestricted legalization of cannabis, the  Canadian government then set limits of the maximum tetrahydrocannabinol (THC) level allowed in a driver’s blood, making it a crime to drive with a blood THC level above 2 nanograms per milliliter. The government also authorized police to screen for impairment at traffic stops and perform THC blood tests in police stations.

However, the researchers determined it is likely the number of auto accident injuries involving cannabis will continue to rise, despite these measures. They called for more studies into cannabis-related driving accidents, and urged the government to consider additional policies, regulations and educational measures to prevent impaired driving and protect the public.

Car Crashes Linked to Drug and Alcohol Use Rise in U.S.

The United States has also seen an increase in auto accidents and accident fatalities related to drug and alcohol use in recent years, as more states pass marijuana legalization laws.

According to a study released in January by the U.S. National Highway Traffic Safety Administration (NHTSA), more than half of all serious and fatal auto accidents involved drug or alcohol use between 2019 and 2021.

Federal highway safety officials indicated that car accident fatalities in the U.S. have consecutively increased over the last few years, contributing to approximately 33,244 deaths in 2019, 38,824 in 2020, and 42,915 in 2021.

The findings also revealed that 55.8% of drivers who sustained severe or fatal injuries in an auto accident tested positive for drug or alcohol use. About a quarter of those drivers tested positive for cannabis, and nearly 20% tested positive for two or more substances.

The researchers in the NHTSA study also recommended that their findings be used to assist in predicting the future impact of impaired driving, and to help form future traffic safety regulations.


  • BrianSeptember 12, 2023 at 9:47 pm

    Bologna. Everybody knows that these bogus so-called "tests" and "studies" can only test for and detect residual trace amounts of THC. Which remain detectable for up to months after actually consuming cannabis. Which in no way whatsoever proves actual impairment at the time of an accident. This is nothing more than desperate prohibitionist lies and Reefer-Madness-like propaganda. Intentionally fabr[Show More]Bologna. Everybody knows that these bogus so-called "tests" and "studies" can only test for and detect residual trace amounts of THC. Which remain detectable for up to months after actually consuming cannabis. Which in no way whatsoever proves actual impairment at the time of an accident. This is nothing more than desperate prohibitionist lies and Reefer-Madness-like propaganda. Intentionally fabricated by prohibitionists with the sole intention of scaring the public away from supporting full federal cannabis legalization nationwide. You aren't fooling, frightening, nor convincing anybody with at least half a brain who can think for themselves and whom has their very own internet access with Google. Legalizing Cannabis will not create a massive influx of marijuana impaired drivers on our roads. It will not create an influx of professionals (doctors, pilots, bus drivers, etc..) under the influence on the job either. This is a prohibitionist propaganda scare tactic. Truth: Responsible drivers don't drive while impaired on any substance period! Irresponsible drivers are already on our roads, and they will drive while impaired regardless of their drug of choice's legality. Therefore, legalizing cannabis will have little impact on the amount of marijuana impaired drivers on our roads. The same thing applies to people being under the influence of cannabis on the job. Responsible people do not go to work impaired, period. Regardless of their drug of choice's legality. What has actually occurred in states that have legalized cannabis is that law enforcement agencies statewide immediately and vigorously began a new policy of testing more drivers than they ever did before legalization occurred for residual trace amounts of THC. Which remain detectable in a driver's system for up to months after consuming cannabis. This obviously in no way proves actual impairment at the time a driver is pulled over. So for instance, the police get to the scene of a roadside accident with a fatality. The driver at fault, is let's say for example three times over the legal alcohol BAC limit, but the police also insist on a test for cannabis. Although bear in mind, with a BAC three times over the legal limit for booze and with all the obvious tell-tale signs of impairment, it's plain for all to immediately see, and know, that alcohol was the drug responsible for this tragedy.... Residual trace amounts of THC are detected in the driver's system after the police conclude their very specific and intentional policy driven test for those residual trace amounts of THC. A month prior to being pulled over, the driver consumed a little cannabis socially with friends... Obviously, the joint or two from a month ago had nothing to do with this fatal and tragic accident, but the booze the driver drank at the bar before he got into his car that very same night most certainly did. Law enforcement now marks off this accident as another cannabis "INVOLVED" fatality in order to bolster their bogus statistics. Prohibitionists always use terms like "INVOLVED" , "RELATED" or "LINKED" when they tout these horrific sounding statistics and claims. Because they can't ever prove cannabis impairment alone to be the actual "CAUSE". In states that have now legalized cannabis, when you get into an accident whether at fault or not at fault even, pulled over for speeding or for anything at all, law enforcement policy will automatically also require that the police administer that very same test for residual trace amounts of THC from up to months prior to being pulled over. Which again, in no way proves impairment whatsoever and then the results are added on as just another one of their bogus cannabis "INVOLVED/RELATED"/LINKED" statistics. This is nothing more than merely another prohibitionist scare tactic. The goal being to frighten and alarm the public back into the strict prohibition of cannabis. Well guess what? The public isn't buying it and everyone sees the deceit by ever more desperate prohibitionist zealots. Hell-bent on keeping cannabis illegal. So, the public is already well aware that when such claims are made about cannabis "INVOLVED/RELATED/LINKED" deaths, they are flat out lies! Nobody is so gullible as to believe these utterly nonsense prohibitionist claims of massive amounts of new cannabis impaired drivers. Now, I challenge all anti-cannabis prohibitionist types publicly yet again: Please provide us proof of just one single roadway fatality proven one hundred percent to have been "CAUSED" (Not "INVOLVED/ Not "RELATED"/Not "LINKED") by cannabis impairment and only cannabis impairment, alone. The public is waiting for prohibitionists to provide indisputable proof of just one such death "CAUSED" directly and solely by cannabis impairment, alone. Just one. (Not even the massive influx prohibitionists claim. Just one.) We'll wait....and wait...and wait....While we all know they simply can't. Because it's all just propaganda, lies, and scare-tactics. *yawns* Next?

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