ONE in three high school students reports riding with a driver who has been drinking, while nearly one in five was in a car where the driver had consumed marijuana, according to a new study from the University of Waterloo.

Researchers at the Propel Centre for Population Health Impact at Waterloo found that 35 per cent of students in Grades 9 to 12 reported riding in cars with drivers who consumed at least one drink within the previous hour. Close to 20 per cent rode in cars with a driver who used marijuana in the previous two hours.

“These numbers are concerning because Canadian youth are at higher risk of death from traffic injuries than any other age group,” said Leia Minaker, lead author on the paper and an assistant professor at Waterloo. “A significant proportion of car-crash deaths are related to alcohol and drug impairment.”

About nine per cent of students in Grades 11 and 12 — or 66,600 teens — have driven within an hour of drinking. A total of 9.4 per cent have driven after using marijuana.

“The link between alcohol-impaired driving and collision rates is well recognized, but the consequences of marijuana use are less clear,” said Minaker. “As legislation is drafted to regulate recreational marijuana over the coming months, the federal government and the provinces need to prioritize keeping marijuana away from kids, and creating strong policies to reduce marijuana-impaired driving.”

The study also found that while boys were more likely to drive after drinking or using marijuana, girls had higher odds of riding with drivers who had been drinking. Students in rural areas are also at a greater risk of drinking and driving than students from urban areas. Students in Saskatchewan had the highest rates of both drinking and marijuana use before driving.

The study was recently published in Canadian Medical Association Journal Open.