Cannabis may increase depression risk among teens

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A new meta-analysis links adolescent cannabis use to an increased risk of depression and suicidal behavior in young adulthood.

The conclusions, published in JAMA Psychiatry, come from a systematic review and meta-analysis of international studies comprising 23,317 individuals. The results reveal that cannabis use in adolescence could harmfully alter mental health, even in teenagers who did not report any depressive symptoms before starting cannabis.

Analysis is lacking on the impact of adolescent cannabis use on the risk of developing depressive symptoms and mood disorders on the adolescent brain, which is still developing until the age of 25.

The risk is particularly elevated in North America, where adolescents have higher rates of cannabis use compared to their peers in other developed countries. Canadian youth aged 15-25 constitute the majority of users of all ages (spanning 20-33 percent) while over 20 percent of adolescents in the United States report monthly use.

Researchers analyzed the risk of depression, anxiety, suicidal ideation, and suicide attempts based on daily-to-occasional cannabis consumption.

“The study suggests the diagnosis of depression in approximately seven percent of Canadians and Americans between the ages of 18-30 is attributable to cannabis, meaning 25,000 young Canadians and 400,000 young Americans suffer from depression because of earlier cannabis consumption,” says coauthor Nancy Mayo, a professor in the department of medicine and School of Physical and Occupational Therapy at McGill University and a scientist at the Centre for Outcomes Research and Evaluation of the Research Institute of the McGill University Health Centre (RI-MUHC).

Researchers reported instead a weaker association with anxiety.

“When we started this study we expected depression to be a factor attributable to cannabis consumption, but we were quite surprised about suicide behavior rates. Indeed, a significant percentage of suicidal attempts are attributable to cannabis,” says Gobbi, who is also an MUHC psychiatrist and a researcher in the Brain Repair and Integrative Neuroscience Program.

The findings highlight the importance of prevention initiatives aimed at educating teenagers on the risks associated with cannabis use while teaching them skills to resist peer pressure.

“It is clear that a lot of young people consuming cannabis are at risk of developing depression and suicidal behavior, so it is very important for authorities to be more proactive in campaigning for prevention,” states Gobbi. “We hope the findings will spur public health organizations to apply preventative strategies to reduce the use of cannabis among youth.”

Coauthors of the study are from the University of Oxford and Rutgers University-Camden.

Source: McGill University