Incidence, risk and protective factors for suicide mortality among patients with major depressive disorder

Aim Patients with major depression have greater suicide mortality, but there is no data on the standardised mortality ratio (SMR) and factors for suicide of major depression for Asian countries. This research estimates the SMR and the risk and protective factors for suicide mortality in patients with major depression in a large-scale Asian cohort. Methods Patients with major depression (N = 1978) admitted to a psychiatric hospital in Taiwan between 1985 and 2008 were enrolled as the study cohort. When the cohort was linked to the national mortality database, 415 deceased patients were identified. Of these 415 deaths, 107 were from suicide. Nested case–control with risk sampling was used, where each case was matched with two controls. Clinical information was collected through a standardised chart review process. The SMR for suicide mortality was estimated, and a conditional logistic regression analysis was performed to determine risk and protective factors for suicide. Results Patients with major depression had high all-cause and suicide mortality, with SMRs of 3.9 and 35.4, respectively. Agitation (adjusted risk ratio [aRR] = 2.85, P = 0.058), restlessness (aRR = 15.05, P = 0.045) and previous suicide attempts (aRR = 4.48, P = 0.004) were identified as risk factors for suicide mortality. By contrast, those with employment (aRR = 0.15, P = 0.003) or loss of interest (aRR = 0.32, P = 0.04) had lower risk. Conclusions Patients with depression exhibited higher suicide mortality. Clinical staff should pay close attention to risk and protective factors to reduce suicide risk.