A new study shows that young people who regularly smoke grass are at greater risk of developing depression and suicidal behavior at a young age.
Scientists from McGill University have analyzed 11 international studies with longitudinal studies involving people aged 18 to 32 who smoked weekly or daily when they were 18 years of age or younger.
They found a higher incidence of diagnosed depression, suicidal ideation and suicide attempts than those who did not use cannabis in their teens.
Leading author Gabriela Gobby says the increased individual risk is modest, but the popularity of the pot means that a large number of young people may be at risk of developing mental health problems.
According to researchers, seven percent of Canadians between the ages of 18 and 30 have been diagnosed with cannabis depression or about 25,000 young people. Researchers have found even stronger links with suicidal ideas and attempted suicide, but with weaker anxiety relationships.
The study consisted of a systematic review and meta-analysis of studies involving 23,317 individuals. This was done in collaboration with Oxford University and Rutgers-Camden University and published on Wednesday in JAMA Psychiatry.
Goby says the findings highlight the need for better education on marijuana risks.
"We need to do more prevention, reduce the number of young people and adolescents who smoke cannabis," McGill's Montreal Professor of Psychiatry, calling for teenagers and parents education.
Most provincial laws limit the use of those 19 or older but about 27% of Canadians aged 15 to 24 years – more than any other age group – have used cannabis in the last three months of 2018, according to the Canadian Statistical Office .
"Since we had legalization, young people continue to smoke as before," says Gobi. – Legalization is not the only answer. We need to do more prevention. "
Gobbi says the included studies have been corrected for any topic that may have shown signs of depression or suicidal tendencies before using a pot.
She says adolescents are particularly vulnerable because their brains do not develop completely until they are 25 years old.
The findings also reject the misconceptions that weekly use of the pot is harmless, she adds, noting that scientists have found that it is impossible to differentiate the 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 up to one month. So smoking the joints is not like having two or three beers on Saturday night, "says Gobi, also a researcher in the brain rehabilitation program and integral neurology at the McGill University Medical Center's Science Institute.
Gobby says there are many more questions to be explored, noting that the study has not looked at alternative ways of consuming cannabis,
She also notes that the topics were teenagers in the 1980s, 90s and 2000s, when the content of THC was relatively low.
"We now have joints that have 10, 20, 30 percent, even more THC content, so we do not know the influence of cannabis we have today on mental health. This is something we must, of course, learn more. "
The study is funded by Canadian health research institutes and the Quebec network for suicide, mood disorders and related disorders.