Longitudinal associations of cannabis and illicit drug use with depression, suicidal ideation and suicidal attempts among Nova Scotia high school students

Objective: To examine associations of cannabis and other illicit drug use with depression, suicidal ideation and suicidal attempts over a two year period during adolescence. Methods: Nine hundred and seventy-six school students in four high schools in northern Nova Scotia, Canada, were surveyed in grade 10 and followed up in grade 12. Assessments of past 30 day cannabis and illicit drug use as well as mental health variables (risk of depression, suicidal ideation and suicide attempts) were obtained at baseline (2000 and 2001) and follow-up two years later (2002 and 2003). Generalized estimating equations modelled depression, suicidal ideation and attempts among illicit drug users and non-users. Results: Illicit drug use with or without cannabis use was significantly associated with higher odds of depression, suicidal ideation and suicide attempt. Heavy cannabis use alone predicted depression but not suicidal ideation or attempt. Conclusions: Illicit drug use, with and without accompanying cannabis use, among high school students increases the risk of depression, suicidal ideation and suicidal attempts. Heavy cannabis use alone predicts depression but not suicidal ideation or attempts.