Cannabis use during adolescence and the occurrence of depression, suicidality and anxiety disorder across adulthood: Findings from a longitudinal cohort study over 30 years

<h4>Objective</h4>To examine the association between cannabis use in adolescence and the occurrence of depression, suicidality and anxiety disorders during adulthood.<h4>Methods</h4>A stratified population-based cohort of young adults (n = 591) from Zurich, Switzerland, was retrospectively assessed at age 19/20 for cannabis use in adolescence. The occurrence of depression, suicidality and anxiety disorders was repeatedly assessed via semi-structured clinical interviews at the ages of 20/21, 22/23, 27/28, 29/30, 34/35, 40/41, and 49/50. Associations were controlled for various covariates, including socio-economic deprivation in adolescence as well as repeated time-varying measures of substance abuse during adulthood.<h4>Results</h4>About a quarter (24%) reported cannabis use during adolescence; 11% started at age 15/16 or younger and 13% between the ages of 16/17 and 19/20. In the adjusted multivariable model, cannabis use during adolescence was associated with adult depression (aOR = 1.70, 95%-CI = 1.24-2.32) and suicidality (aOR = 1.65, 95%-CI = 1.11-2.47), but not anxiety disorders (aOR = 1.10, 95%-CI = 0.82-1.48). First use at age 15/16 and younger (as against first use between age 16/17 and 19/20 and no use) and frequent use in adolescence (as against less frequent use and no use) were associated with a higher risk of depression in adult life.<h4>Conclusions</h4>In this longitudinal cohort study over 30-years, cannabis use during adolescence was associated with depression and suicidality in adult life. Young age at first use and high frequency of use in adolescence may particularly increase the risk of depression in adulthood. All associations were independent of cannabis abuse and other substance abuse during adulthood.