Photo: Unsplash / Omotayo Tajudeen
THC – the intoxicant found in marijuana – is detected in twice as many injured drivers since cannabis was legalized in Canada, according to new research from UBC published in the New England Journal of Medicine.
The findings may indicate that more Canadians are choosing to drive after using cannabis, researchers said.
“It is concerning that we are seeing such a dramatic increase,” said Dr. Jeffrey Brubacher, associate professor in UBC’s Department of Emergency Medicine and principal investigator of the study.
“There are serious risks associated with driving after consuming cannabis. Our findings suggest more is needed to deter this dangerous behavior in light of legalization,” he said.
Brubacher and his colleagues analyzed blood samples from 4,339 moderately injured drivers treated at four trauma centers in British Columbia between 2013 and 2020.
Before the legalization of cannabis, 3.8% of drivers had blood levels of THC above the Canadian legal driving limit of 2 nanograms/ml, according to a study.
This percentage increased to 8.6% after legalization. The proportion of drivers with higher concentrations of THC (above 5 nanograms/ml) also increased, from 1.1% before legalization to 3.5% after.
The biggest increase is for drivers over 50.
There was no significant change in the number of drivers testing positive for alcohol, alone or in combination with THC.
When cannabis was legalized in October 2018, the federal government amended the Criminal Code, giving police more power to test drivers if they reasonably suspect the person has drugs in their body or has committed a drug-impaired driving offence.
Many provinces have followed suit by introducing new penalties, such as fines and license suspensions, to deter cannabis-impaired driving.
Brubacher said research shows these changes are clearly not enough.
“We hope policymakers will use our findings to design public education campaigns and enforcement actions that encourage drivers, especially older drivers, to separate cannabis use from driving,” Brubacher said. “At the same time, it’s important not to lose sight of alcohol-impaired driving, which poses an extremely high risk, especially when combined with cannabis.
Blood THC levels typically peak at over 100 nanograms/ml within 15 minutes of cannabis use, but quickly drop to less than 2 nanograms/ml within four hours of consumption, the team said. research. After ingesting edible forms of THC, levels drop to an equally low concentration after eight hours.
Although cannabis use is associated with cognitive deficits and psychomotor disorders, Brubacher cautions that the presence of THC in the blood is not always an indicator that a crash was caused by cannabis tampering.
Brubacher’s team is now expanding the research to 15 trauma centers across Canada, studying the prevalence of cannabis, alcohol and other impairing substances among injured drivers.