BACKGROUND: Severe unipolar depression is associated with increased risk of suicide, but it remains unknown whether the same risk factors are present in the non-psychotic (non-PD) and psychotic (PD) subtypes respectively. Therefore, this study aimed to identify risk factors for suicide in non-PD and PD separately, and to investigate if the presence of psychotic symptoms is an independent risk factor for suicide in severe depression.

METHODS: This register-based, nationwide, historical prospective cohort study used logistic regression analyses to ascertain risk factors for suicide among all adults diagnosed with severe depression at Danish psychiatric hospitals between January 1, 1994 and December 31, 2010. The risk for suicide was expressed as adjusted odds ratios (AOR).

RESULTS: A total of 34,671 individuals with severe depression (non-PD: n=26,106 and PD: n=12,101) were included in the study. Of these, 755 completed suicide during follow up. PD was not found to be an independent risk factor for suicide in severe depression (AOR=0.97 [0.83-1.15]). Older age (non-PD AOR=1.05 [per year], PD AOR=1.04 [per year]), male sex (non-PD AOR=1.89, PD AOR=1.98), and a previous incident of self-harm (non-PD AOR=5.02, PD AOR=5.17) were significant risk factors for both groups.

LIMITATIONS: As the study population was comprised only of patients with contact to psychiatric hospitals, the results cannot be extrapolated to the primary care setting.

CONCLUSION: The following risk factors for non-PD and PD were identified: older age, male gender and previous incidents of self-harm. In suicide prevention efforts, equal attention should be paid to non-PD and PD patients.