Just as many teenagers use cannabis every day as smoke cigarettes, according to a new report from the Propel Centre for Population Health Impact at the University of Waterloo.

The report, published as a supplement to Tobacco Use in Canada: Patterns and Trends, found that two per cent of Canadian students in Grades 7 to 12 – equivalent to more than 43,000 students – use marijuana every day. Daily smoking is similar at 1.8 per cent, according to the Canadian Student Tobacco, Alcohol and Drugs Survey.

Occasional cannabis use remains high among youth: one in five students reports ever trying it, and one in 10 reports use in the last 30 days.

“Although Canadian youth are less likely to try marijuana than they were a decade ago, the number using on a daily basis is surprisingly high,” said David Hammond, a professor in the School of Public Health and Health Systems at Waterloo and co–author of the supplement.

The report also found a strong association between tobacco use and marijuana consumption. More than 90 per cent of students in Grade 7 to 12 who were current smokers also reported ever trying cannabis. Close to nine per cent – or 155,000 students – who have never tried a cigarette have tried cannabis.

Patterns of co–using tobacco and cannabis have changed dramatically over the past 20 years. In 2011, 92 per cent of tobacco users reported also using cannabis, compared to 16 per cent in 1991.

“This clustering of marijuana and tobacco use is a concern,” said Hammond. “It is a myth that marijuana smoke is less harmful to inhale than tobacco smoke. Marijuana smoke contains many of the same carcinogens as cigarette smoke. Marijuana use through other, non–smoked forms can reduce the harm from chronic use.”

The health effects associated with cannabis depend on three primary factors: the frequency of use, age of initiation, and use among high–risk groups or settings. Early initiation and heavier use of cannabis among youth is consistently associated with more severe long–term negative outcomes.

“As the federal government prepares to legalize marijuana in 2018, it should consider ways of de–coupling smoking and marijuana, to reduce the direct harm from marijuana use, but also to ensure that legalization doesn’t undermine reductions in youth smoking,” said Hammond.