Rationale: Our brains undergo a crucial stage of development during adolescence. Major depressive disorder and suicide are especially common during this time. Evidence shows that cannabis use is twice as common among adolescents with MDD. Researchers studied the possible connection between cannabis use and depressive and suicidal behaviour.     

Method: 10,100 adolescents aged 13-18 years with lifetime cannabis use were studied. Participants were evaluated for severity of cannabis use, from occasional to heavy usage. 

Results: Compared to non-users, teens who used cannabis more than three days a week were: twice as likely to have mild or moderate depression, 2 ½ times as likely to have severe depression, and up to eight times more likely to attempt suicide. Teens who had EVER used cannabis were also about: three times more lilkely to have suicidal thoughts, almost four times more likely to have made a suicide plan, and nearly seven times more likely to have attempted suicide. Among cannabis users, starting at an older age lowered the risk of attemping suicide by about 15% for each additional year of delayed use. 

Meaning: Cannabis use during teen years is strongly linked to both depression and suicidal thoughts or behaviors. The more often and heavily teens use cannabis, the higher the risk for serious depression and suicide attempts. It is important to have screening, early help, and prevention programs in schools and mental health settings to address cannabis use among teens