Cannabis use, depression and suicidal ideation in adolescence: direction of associations in a population based cohort

Journal of Effective Disorders

Research has shown a link between cannabis use and depression. It remains unclear, however, whether depression leads to cannabis use or cannabis use leads to depression. They could also causally influence each other or lack a causal link altogether.

This study aimed to shed light on how cannabis use and depression influence each other over time. They assessed cannabis use, depressive symptoms, and suicidal thoughts from over 1600 adolescents from the province of Quebec at three ages: when they were 15, 17, and 20 years old. Perhaps unsurprisingly, the researchers found that cannabis use was highly associated across time points. In other words, if a participant used cannabis weekly at age 15, they were much more likely than other participants to use cannabis weekly at age 17 and 20. The same held true for depressive symptoms and suicidal thoughts across the three ages.

The researchers found evidence to support two other associations across time. First, 15-year-olds who used cannabis weekly were somewhere between as likely to five times more likely to seriously consider suicide by age 17. The analysis suggests, however, that alternate factors such as alcohol, tobacco, and other drug use drive this relationship. Second, the 10% of participants with the highest score of depressive symptoms at age 15 were about twice as likely to use cannabis at age 17. This association remained true after accounting for socioeconomic status and other substance use.

There was no evidence to support any other associations with cannabis use over time. For example, depressive symptoms at age 17 did not help predict cannabis use at age 20 and cannabis use at age 17 did not help predict depressive symptoms at age 20.

Notably, the researchers did not have information concerning the potency of the cannabis used or the frequency of use and all other information was self-reported. Nonetheless, this study provides evidence that cannabis use in early adolescence may contribute to depressive symptoms in later adolescence.

Read the original article here.

Bolanis, D., Orri, M., Castellanos-Ryan, N., Renaud, J., et al. Cannabis use, depression and suicidal ideation in adolescence: direction of associations in a population based cohort. Journal of Affective Disorders. vol 274, pp. 1076-1083. https://doi.org/10.1016/j.jad.2020.05.136.