No previous study has prospectively investigated incidence and risk factors for suicide attempts among primary care patients with depression.

In the Vantaa Primary Care Depression Study, a stratified random sample of 1119 patients was screened for depression, and Structured Clinical Interviews for DSM-IV used to diagnose Axis I and II disorders. A total of 137 patients were diagnosed with a DSM-IV depressive disorder. Altogether, 82% of patients completed the 5-year follow-up. Information on timing of suicide attempts, plus major depressive episodes (MDEs) and partial or full remission, or periods of substance abuse were examined with life charts. Incidence of suicide attempts and their stable and time-varying risk factors (phases of depression/substance abuse) were investigated using Cox proportional hazard and Poisson regression models.

During the follow-up there were 22 discrete suicide attempts by 14/134 (10.4%) patients. The incidence rates were 0, 5.8 and 107 during full or partial remission or MDEs, or 22.2 and 142 per 1000 patient-years during no or active substance abuse, respectively. In Cox models, current MDE (hazard ratio 33.5, 95% confidence interval 3.6–309.7) was the only significant independent risk factor. Primary care doctors were rarely aware of the suicide attempts.

Of the primary care patients with depressive disorders, one-tenth attempted suicide in 5 years. However, risk of suicidal acts was almost exclusively confined to MDEs, with or without concurrent active substance abuse. Suicide prevention among primary care patients with depression should focus on active treatment of major depressive disorder and co-morbid substance use, and awareness of suicide risk.