Marijuana-Related Auto Accident Injuries Doubled After Legalization in Canada, Study Warns

Canadian researchers have found that the rates of automobile accident injuries involving drivers under the influence of marijuana more than doubled after legalization of the drug in that country.

The study was published this week in the New England Journal of Medicine, indicating that the number of drivers injured in marijuana-related automobile accidents increased 115% in Canada since it was legalized.

Even though Canada has set a 2 ng per milliliter tetrahydrocannabinol (THC) limit for driving, one of the challenges many highway officials face is that there is no defined method for testing a driver’s cognitive or motor skill performance for drug impairment roadside at the time of a car crash or traffic stop.

Researchers reviewed British Columbia trauma center data from January 2013 through March 2020, specifically looking at drivers warranting a blood test following a car accident injury. The study identified a total of 4,339 drivers meeting the criteria, in which 3,550 were before the legalization of marijuana in October 2018, and 789 after legalization.

Prior to October 2018, researchers found that 9.2% of drivers had THC levels greater than 0, with 3.8% having THC levels above 2 ng per milliliter, and 1.1% driving with THC levels over 5 ng per milliliter. However, those numbers drastically increased in the data set following marijuana legalization in Canada, with percentages jumping to 17.9%, 8.6%, and 3.5%, respectively.

Researchers say they also found a significant increase in motor vehicle accident injuries involving drivers with THC prevalent in their system greater than 0 ng per milliliter.

Older drivers, specifically men, were the drivers most often involved in the THC impaired car crashes, according to the findings. The study did not find any significant changes in drivers testing positive for alcohol impairment after marijuana legalization.

Impaired Driving Automobile Accidents

Alcohol and drug impaired car accidents account for nearly a quarter of the annual traffic fatalities each year. In the United States, the National Highway Traffic Safety Administration (NHTSA) recorded that an estimated 38,680 people died in all traffic crashes in 2020, while over 10,000 of those fatal crashes involved a driver with an illegal Blood Alcohol Concentration (BAC) of .08 or greater.

The recreational use of cannabis has been legalized in at least 18 states and the District of Columbia, with at least another 13 having decriminalized marijuana use. While many states have changed their positions on marijuana regulation, prior studies have shown an upward trend in the number of drunk and/or drugged driving automobile fatalities and injuries, with a national average of approximately 10,500 fatalities annually.

A recent study conducted by the U.S. Centers for Disease Control and Prevention found that 5% of the population in the U.S. admits to driving while under the influence of marijuana. That equates to roughly 12 million Americans over the age of 16 being high while driving.

In January 2020, research from McLean Hospital in Belmont, Massachusetts was published in the journal Drug and Alcohol Dependence, finding marijuana impaired drivers struck pedestrians, went over the speed limit more often, made fewer stops at red lights, and crossed the center line more often during the simulation compared to people who didn’t use marijuana at all.

The driving simulation found marijuana users demonstrated impaired driving compared to non-users, even though they were sober. They consistently performed worse on the driving simulations than non-users.