Cannabis impairs driving ability up to five hours after consumption: study
With legalization only hours away, new research conducted by McGill University, paid for by the Canadian Automobile Association, is showing how cannabis consumption can affect your ability to drive.
As part of the study, young adults got behind the wheel of a driving simulator after inhaling the equivalent of less than one joint.
Using a medical grade vaporizer, 45 recreational marijuana users between the ages of 18 and 24 consumed 100 milligrams of dried cannabis before taking the test.
They were also tested with no cannabis in their system as a comparison.
After using cannabis, the McGill study found participants were for the most part able to safely navigate the virtual roadways without any major problems braking, steering or maintaining a steady speed.
Once they were exposed to more complicated everyday driving tasks such as hazards on the road and crossing busy intersections researchers say their performance got worse and the risk of a collision increased, even up to five hours after consuming cannabis.
"Our drivers or participants were impaired in driving-related tasks, especially in complex tasks,” said study co-author Isabelle Gélinas, a researcher in McGill University’s School of Physical and Occupational Therapy.
While previous studies have shown cannabis can affect braking and reaction time, researchers say this study substantiates recommendations in Canada's Lower-Risk Cannabis Use Guidelines to wait six hours after consuming marijuana before driving.
"The main recommendation is if you smoke cannabis you shouldn't drive and you should not take the wheel until more than five hours,” said Gélinas. “We didn't go beyond but some guidelines recommend six hours.”
According to numbers provided by Manitoba Public Insurance there were eight collisions reported by police in Manitoba last year related to drug-impaired driving including a crash which left one person dead.
CAA said polls have shown one in five young drivers believe their ability to operate a motor vehicle is as good or better after using cannabis.
The organization said the results of the study suggest they’re wrong.
"At all points throughout the study those participants said they didn't feel safe to drive which is a really big takeaway and a piece of food for thought for Canadians,” said Erika Miller, a communications consultant with CAA Manitoba.
The study focused on young people because the researchers said they are already at a higher risk of being involved in collisions and are also the age group most likely to use cannabis.
Both researchers and CAA said further studies are needed to better understand how cannabis affects drivers.
Under the Criminal Code, a first offence for drug-impaired driving involving five or more nanograms of THC per millilitre of blood could lead to a minimum fine of $1000, up to five years in custody as well as driving suspensions.
Manitoba's Justice Minister Cliff Cullen said police are ready to enforce the law but he said the challenge is getting the message to drivers.
"That's why we have a multi-pronged education program underway to try to make sure that Manitobans understand the risks associated with cannabis use and impaired driving," said Cullen.