Canadian study links teenage pot use to increased risk of suicidal behaviour

Scientists at McGill University found a higher rate of diagnosed depression in young cannabis users

A new study suggests teens who regularly smoke weed are at greater risk of developing depression and suicidal behaviour in young adulthood.

Scientists at McGill University analyzed 11 international longitudinal studies involving people aged 18 to 32 who smoked weekly or daily when they were 18 or younger.

They found a higher rate of diagnosed depression, suicide ideation and suicide attempts compared to those who didn’t use cannabis in their teens.

Lead author Gabriella Gobbi says the increased individual risk is modest, but the popularity of pot means a large number of young people could be at risk of developing mental-health issues.

Researchers estimate seven per cent of Canadians between the ages of 18 and 30 are diagnosed with depression that could be linked to prior cannabis use, or roughly 25,000 young people. Researchers found even stronger links to suicidal ideation and suicide attempt, but weaker links to anxiety.

The study consisted of a systematic review and meta-analysis of studies comprising 23,317 individuals. It was done in collaboration with Oxford University and Rutgers University-Camden and published Wednesday in the journal JAMA Psychiatry.

Gobbi says the findings highlight the need for better education on the risks of marijuana.

“We have to do more prevention, to decrease the amount of young people and adolescents that smoke cannabis,” the McGill psychiatry professor says from Montreal, urging education for teens and parents.

Most provincial laws restrict usage to those 19 and older, but about 27 per cent of Canadians aged 15 to 24 — more than any other age group — used cannabis in the last three months of 2018, according to Statistics Canada.

“Since we had legalization, young people continue to smoke as before,” says Gobbi. “So legalization is not the only response. We need to do more prevention.”

Gobbi says the studies included were adjusted for any subjects that may have displayed signs of depression or suicidal tendencies before using pot.

She says adolescents are particularly vulnerable because their brain does not fully develop until age 25.

The findings also dispel misconceptions that weekly pot use is harmless, she adds, noting that scientists found it impossible to differentiate degree of risk between weekly use and daily use.

She explains that the psychoactive property in cannabis — tetrahydrocannabinol, or THC — remains in the body “for a long, long time.”

“THC is a lipid so it stays in the brain and in the body for one week or even more — in some individuals until one month. So smoking a joint is not like drinking two or three beers on a Saturday night,” says Gobbi, also a researcher in the Brain Repair and Integrative Neuroscience program at the Research Institute of the McGill University Health Centre.

Gobbi says there are many more questions to explore, noting the research did not consider alternate modes of consuming cannabis such as vaping or edibles.

She also notes the subjects were teens during the 1980s, 1990s, and 2000s, when the amount of THC content was generally relatively low.

“Now we have joints that have 10, 20, 30 per cent, even more content of THC so we don’t know the impact of the cannabis that we have today on mental health. This is something that of course we have to study more.”

The research was funded by the Canadian Institutes of Health Research and the Quebec Network on Suicide, Mood Disorders and Related Disorders.

If you or anyone you know needs support for depression or suicide-related mental health problems, call the Canadian Assistance in Suicide Prevention 24/7 hotline at 1-888-353-2273.

Cassandra Szklarski, The Canadian Press

Like us on Facebook and follow us on Twitter.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Flights from Quesnel not cleared for takeoff

Central Mountain Air’s schedule until at least Oct. 31 does not include any Cariboo stops

COVID-19 forces Quesnel 4-H auction outside

The auction has moved outdoors and allowed for proxy bidding to accommodate social distancing

Quesnel opens loop and bridge after flooding receeds

The Johnston Bridge is now open to traffic from both directions

Quesnel cemetery damaged by bears

Some Tranquility Gardens memorial trees were heavily damaged by a family of bears looking for food

Canucks ride momentum into NHL playoff series against defending Stanley Cup champs

PREVIEW: Vancouver opens against St. Louis on Wednesday

Man, 54, charged in connection with fatal attack of Red Deer doctor

Doctor was killed in his walk-in clinic on Monday

One dead as fish boat sinks off southern Vancouver Island

Shawnigan Lake-registered Arctic Fox II went down off Cape Flattery, west of Victoria

Landlord takes front door, windows after single B.C. mom late with rent

Maple Ridge mom gets help from community generosity and government

42 more people test positive for COVID-19 in B.C.

The province has recorded no new deaths in recent days

Joe Biden selects California Sen. Kamala Harris as running mate

Harris and Biden plan to deliver remarks Wednesday in Wilmington

Lawsuit launched after Florida child handcuffed, booked and briefly jailed

Suit alleges “deliberate indifference” to what should have been handled as a behavioural issue

Russia approves vaccine, Putin hopes to begin mass production

Critic calls decision to proceed without thorough testing ‘dangerous and grossly immoral’

Most Read