Addiction experts caution Liberals over plan to legalize marijuana, citing latest research that dispels the 'harmless' myth

By Bill Kaufmann,

CALGARY - Substance abuse experts on Friday urged caution over Ottawa's plans to legalize marijuana.

Two members of a panel speaking in Calgary said updated research on how regular marijuana use negatively affects adolescents in numerous ways should colour the debate over the cannabis legalization promised by the new Liberal government.

Knowledge that cannabis affects the developing brain until age 25 should influence any legalization age restrictions, said Dr. Philip Tibbo, director of the Nova Scotia Early Psychosis program.

"With a drinking age at, say, 18, does that mean we have to have the same age for cannabis as well?" said Tibbo.

The increasing content of cannabis' active ingredient, THC, complicates regulating the drug, said Dr. Franco Vaccarino, a chairman of the Canadian Centre on Substance Abuse (CCSA) which hosted Friday's discussion.

"What percentage of THC are we talking about?" said Vaccarino.

"Given the increasing amount of knowledge, we owe it to ourselves to elevate the conversations — there's not one simple thing we're talking about in legalization."

Vaccarino said a trend in the 1980s to view drug risks seriously led to lower use of certain substances and a dark public perception of their use.

That has since been reversed, he added.

"In this world of unprecedented access to information, it's ironic that there's so much misinformaton," said Vaccarino, who noted that, amid Canada's marijuana prohibition, the country has one of the highest rates of use among developed countries.

The panel said the latest research debunks numerous myths of cannabis' harmlessness while highlighting the damage it causes to adolescent brains during their crucially formative years.

Some of those impacts can be seen in academic results, said Tibbo.

"You can measure that in test scores and even the ability to finish high school and move to post-secondary education," he said.

"There are definite patterns in changes in brain structure...it's the long-term effects we're more concerned about.

Marijuana use among Canadians aged 15-24 ranges from 22% to 26% with the highest rates among those in the older age brackets, states the CCSA.

In past-year use, 40% of young people admitted misusing alcohol while the number for cannabis was 19% and 4% for pharmaceuticals.

Social acceptance of marijuana use, particularly among the young, has reached troubling proportions driven largely by the discussion surrounding it, said Dr. Kim Corace of the Royal Ottawa Mental Health Centre.

"In my discussions with them, they believe marijuana use is already legal," she said.

Cannabis use is also known to contribute to mental health disorders in young people, particularly those already pre-disposed to them, said Corace.

"Those who do use cannabis are at greater risk of developing depression, and earlier," she said.

Four U.S. states have legalized marijuana with several others leaning in that direction.