McGill study links pot to depression in teens
Teens and young adults who consume cannabis are at an increased risk of depression and suicidal behaviour, suggests a new analysis by a team of researchers at McGill University.
The study follows an awareness campaign by the Quebec government last week that highlighted the risks of smoking pot among young Quebecers. That campaign observed that the brain continues to develop until the age of 25, making teens and young adults more vulnerable to the effects of cannabis.
The McGill study suggests that smoking pot can be linked to depression in about seven per cent of Canadians and Americans between the ages of 18 and 32. That works out to about 25,000 young Canadians and 400,000 young Americans who suffer from depression because of earlier daily or occasional use of cannabis.
The study also warns of a significant increase in the risk of suicidal ideation in teens and young adults who are already susceptible to suicidal behaviour.
“Pre-adolescents and adolescents should avoid using cannabis as use is associated with a significant increased risk of developing depression or suicidality in young adulthood,” the study concludes. “These findings should inform public health policy and governments to apply preventive strategies to reduce the use of cannabis among youth.”
The results were published Wednesday in the journal JAMA Psychiatry and are based on a review of nearly a dozen international studies comprising more than 23,000 individuals. The researchers, including colleagues at Oxford University and Rutgers University-Camden, did observe a weaker association between cannabis and anxiety.
“When we started this study, we expected depression to be a factor attributable to cannabis consumption, but we were quite surprised about suicide behaviour rates. Indeed, a significant percentage of suicidal attempts are attributable to cannabis,” Dr. Gabriella Gobbi, a psychiatrist at McGill and the lead author of the paper, said in a statement.
In an interview, Gobbi explained that “if you have some risk of suicidal ideation, cannabis increases your risk by 50 per cent.”
“Each person is different. If you have a risk of suicidal behaviour of three per cent, cannabis will increase that risk to maybe 4.5 per cent.”
Gobbi lauded Quebec for launching its awareness campaign.
“Absolutely,” she said, “because what we know about a lot of studies on prevention is that prevention of marijuana works. The more you do in terms of prevention, the more you will decrease the quantity of young people that smoke cannabis and you will decrease the rate of depression later on.”
Gobbi disputed the notion that cannabis is innocuous because it’s derived from a plant.
“It’s not because cannabis is a plant that it’s harmless or dangerous,” she added. “Cannabis with the concentration of THC that we have today — which is more than 10 per cent — can be dangerous for the brain, and there is some risk of possibly developing depression and suicidal behaviours.”
Although Ottawa legalized the recreational use of cannabis on Oct. 17, 2018, medical associations across Canada have raised a number of health concerns about its consumption.
Since the Coalition Avenir Québec was elected to a majority government on Oct. 1, it has tabled Bill 2, which would raise the cannabis consumption age from 18 set by Ottawa to 21.
Gobbi is to testify next week at hearings on the subject at the National Assembly.
If you have some risk of suicidal ideation, cannabis increases your risk by 50 per cent.