Marijuana more risky for teens than previously thought

As the debate about legalizing marijuana heats up in Canada, a new study suggests the drug might beriskier forteens to consumethan had been previously thought.

Researchers from the Universit de Montral and New York's Icahn School of Medicine at Mount SinaiHospital conducted a review of 120 studiesexamining cannabisand teenage brain development, and concluded there is strong evidence early cannabis use puts some teens at risk ofdeveloping addictionand mental health problems as adults.

• Politicians and pot: Notable public figures who admitted to smoking marijuana

Dr. Didier Jutras-Aswad,with the Universit de Montral's psychiatry department, is a co-author of the review, which waspublished this month in the journalNeuropharmacology. He says that in adolescence, the brain is still fine-tuning how different areas, such as learning and memory, interact and it appears that marijuana use alters that process.

"When you disrupt this, actually, development, during adolescence, notably through cannabis use, you can have very pervasive, very negative effects in the long-term, including on mental health and addiction risk," he told CBC News.

'The question is not about whether cannabis is good or bad, but who is more likely to suffer from problems.' Dr. Didier Jutras-Aswad,Universit de Montral

Some studies have also found links between earlycannabis use and schizophrenia, but Jutras-Aswad says it seems clear there is a wide risk profilethatincludes genetics and behavioural traits in addition to age.

"For me, the question is not about whether cannabis is good or bad, but who is more likely to suffer from problems in cannabis, because we know for most people that will not happen," he said.

However, the study's authors point out that there is a widespread perception that marijuana is of little harm and the current discussions about access, such asLiberal Leader Justin Trudeau's calls for legalization,ignore the drug's impact on vulnerable populations in particular, teenagers.

• Trudeau's pot 'actions speak for themselves,' Harper says

Vancouver pot activist Jodie Emery says she questions how conclusive the evidence about cannabis's harmful effects on the teenage brain is, but also says legalization for adults doesn't have to mean open access for youth.

"We're not saying legalize marijuana for teenagers. That's not the message here. That's not what we're talking about. We're saying legalize it for responsible adults, who are right now being arrested and persecuted," Emery said.