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A New Study Confirms Cannabis and Driving Don’t Mix

By AMA Staff

Some Canadians don’t think it’s dangerous to drive while high, but a recent CAA-funded study by McGill University confirms just how hazardous it can be.

Researchers found that young drivers’ ability to perform tasks—including merging, crossing an intersection and maneuvering among multiple vehicles—was negatively affected even five hours after they’d consumed cannabis.

Polling conducted by CAA has found that one in five young Canadians believe they are as good or better drivers stoned as they are sober. The McGill study is therefore a sobering counterpoint to that notion.

Participants in the clinical trial were recreational cannabis users between the ages of 18 and 24. Their driving performance was evaluated on four different days using a state-of-the-art driving simulator and a Useful Field of View test. Testing was randomized to occur one hour, three hours and five hours after the subjects had consumed a vaporized 100 mg dose of dried cannabis—notably less than a typical joint, which contains 300 to 500 mg of the drug.

The study was carried out last year by a multidisciplinary team at the Centre for Innovative Medicine, a division within the world-renowned Research Institute of the McGill University Health Centre.

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While further research is needed on a broader range of drivers, these findings add to the already strong evidence that cannabis use and driving do not mix.

“The facts are clear: your crash risk can be doubled when you’re high on cannabis and you choose to get behind the wheel,” says Jeff Kasbrick, AMA’s vice-president of government and stakeholder relations. “Combine cannabis with alcohol and that can skyrocket to 200 times the crash risk.”

Last fall, AMA launched its own cannabis-impaired awareness campaign. Driving high is a DUI.

“This campaign is all about non-judgment,” says Kasbrick. “We are not trying to give any opinion as to what people choose to do on their own time. All that we’re saying is this: Be responsible when it comes to driving, separate any substance use from the task of getting behind the wheel. You owe it to yourself and everyone around you to drive safe. Cannabis, we know, affects your coordination, your attention span, your reaction time, decision-making­—all very important things when it comes to driving—so it’s important to separate the two.”

The complete, peer-reviewed study can be viewed online at CMAJ Open, an online sister publication of the Canadian Medical Association Journal.