Cannabis use can affect the ability of young people to perform some tasks related to driving, a study in Canada found. Researchers at McGill University in Montreal, Quebec, discovered that drivers 18-24 years old performed complex driving tasks less successfully up to five hours after consuming cannabis. The study was funded by the Canadian Automobile Association and published in the Canadian Medical Association Journal.
For the study, researchers used a simulator to study the driving abilities of 45 recreational cannabis users aged 18-24. Participants were tested before using cannabis and again one, three, and five hours after vaporizing a 100-milligram dose of cannabis with a THC content of 12.9 percent.
“Performance was almost always significantly better without cannabis,” the authors of the study wrote.
Researchers found that cannabis did not appear to affect simple driving tasks such as steering, braking, and maintaining a steady rate of speed. But when participants were asked to perform more complex driving tasks such as noticing multiple traffic hazards, they did not do as well after using cannabis.
“Among young recreational cannabis users, a 100-mg dose of cannabis by inhalation had no effect on simple driving-related tasks, but there was significant impairment on complex tasks, especially when these were novel. These effects, along with lower self-perceived driving ability and safety, lasted up to 5 hours after use,” the study reads.
But Risk Of Collision For High Drivers ‘Not Significantly Different’
However, the researchers did not find that stoned drivers were more likely to cause a traffic collision.
“On the simulator, an individual’s crash risk on complex driving tasks after each cannabis use session was not significantly different from crash risk with no cannabis use,” according to the study.
And although drivers’ performance on almost all driving tasks decreased after cannabis use, researchers found evidence that high drivers were more vigilant.
“The only exception was for vigilance at 1 hour after cannabis use: vigilance was higher at that time point than for the non-cannabis state. This finding is congruent with the findings of others who have reported an increase in vigilance or caution among participants who drove after cannabis use,” the researchers wrote.
The researchers also studied the subjects’ perception of their driving abilities and safety. Nearly all, 43 out of 45, said that they believed that they were less capable drivers and felt less safe behind the wheel one hour after consuming cannabis. After three hours, three of the participants said that they no longer felt that way and after five hours four more believed that their abilities had returned to normal.
With the legalization of recreational cannabis coming to Canada this week, some fear that the country is headed for an increase in the number of stoned drivers on the road. Another recent study commissioned by the Canadian Automobile Association found that nearly two million drivers in Ontario have driven while under the influence of cannabis.
Jeff Walker, the chief strategy officer of the Canadian Automobile Association, said that drivers concerned about impaired drivers should practice defensive driving techniques.
“The best advice I can give is to make sure that we’re always driving safely. That’s the best path,” Walker said.