Neurology Central

Risk of depression linked to cannabis use in teens

Cannabis has been reported as being the most commonly used drug of abuse by adolescents in the world. Although the impact of adolescent cannabis use on the development of psychosis has gained a lot of focus, there has been less attention on the impact of cannabis on mood and suicidality in young adulthood.

Researchers from the University of Oxford (UK) and McGill University (Montreal, Canada) have carried out a systematic review and meta-analysis of 23,317 individuals (from 11 international studies) to see whether the use of cannabis in young people is associated with depression, anxiety and suicidality in early adulthood.

Within the study, which has been published in JAMA Network, the investigators revealed that adolescent cannabis use was associated with an increased risk of depression and suicidal behavior later in life, even in the absence of a premorbid condition. The researchers noted that there was no association with anxiety.

Individual-level risk was found to be modest, however, the widespread use of cannabis by young adults makes the scale of the risk much more serious. The population attributable risk was found to be approximately 7%, which translates to more than 400,000 adolescent cases of depression that are potentially attributable to cannabis exposure in the USA, 25,000 in Canada and approximately 60,000 in the UK.

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Andrea Cipriani (University of Oxford) commented: “We looked at the effects of cannabis because its use among young people is so common, but the long-term effects are still poorly understood. We carefully selected the best studies carried out since 1993 and included only the methodologically sound ones to rule out important confounding factors, such as premorbid depression.”

“Our findings about depression and suicidality are very relevant for clinical practice and public health. Although the size of the negative effects of cannabis can vary between individual adolescents and it is not possible to predict the exact risk for each teenager, the widespread use of cannabis among the young generations makes it an important public health issue.”

Cipriani added: “Regular use during adolescence is associated with lower achievement at school, addiction, psychosis and neuropsychological decline, increased risk of motor vehicle crashes, as well as the respiratory problems that are associated with smoking.”

To conclude their findings, the researchers indicated that although individual-level risk remains moderate to low, and results from this study should be confirmed in future prospective studies, the high prevalence of adolescents consuming cannabis generates a large number of young people who could develop depression and suicidality attributable to cannabis.

Sources: Gobbi G, Atkin T, Zytynski T et al. Association of cannabis use in adolescence and risk of depression, anxiety, and suicidality in young adulthood. JAMA Network doi:10.1001/jamapsychiatry.2018.4500 (2019) (Epub ahead of print);