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Existing association between mental disorders and suicidality is mostly based on cross- sectional studies, using clinical samples.
Objective and methods
We examined the patterns of association between mental disorders and subsequent suicide in a representative sample of the Canadian household population. This is a retrospective cohort study that used data from the Canadian Community Health Survey 2002 linked to the Death Database 2000-2011 and the Hospitalization Database 1999/2000-2012/2013) (N=27,000). Mental disorders (past-year major depressive episodes (MDE), bipolar disorders (BPD), anxiety disorders (AD), and substance-dependent (SD)) were diagnosed in the survey data using the Composite International Diagnostic Interview. Subsequent suicide events (deaths/hospitalizations for suicide attempts) were identified using ICD-10-CA codes. Time-to-event data were analyzed using competing-risk regression models, adjusting for age, sex, marital status, and educational attainment. Due to the violation of the proportional hazard assumption, the models were stratified into two strata. Sampling weights were used to ensure representation of the target population.
Of 27,000 respondents, mental disorders were diagnosed in 15.0% respondents and 0.4% had suicide events. Each mental disorder was significantly associated with an increased risk of suicide. The strength of association between mental disorder and suicide weakened over-time for MDE, SD, but not for BPD and AD. For example, using the time-to-event cut-off 4-year, the hazard ratio (HR) for MDE was 6.02 (95% CI=2.65,13.68) in the first 4-year, whereas, it was 2.03 (95% CI=0.91,4.53) after 4-year. The HRs of suicide for BPD were 16.95 (95% CI=6.88,41.75) and 15.81 (95% CI=5.89,42.45) before and after 4-year.
Findings reflect improvement of suicide-risk over-time for people with MDE and SA and the persisting risk for people with BPD and AD. Our findings underscore the importance of early management of mental disorders for effective suicide prevention, and requirement of longer-term follow-up for people with BPD and AD.
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