Although suicidal behavior is very common in bipolar disorder (BD), few long-term studies have investigated incidence and risk factors of suicide attempts (SAs) specifically related to illness phases of BD.

We examined incidence of SAs during different phases of BD in a long-term prospective cohort of bipolar I (BD-I) and II (BD-II) patients and risk factors specifically for SAs during major depressive episodes (MDEs).

In the Jorvi bipolar study (JoBS), 191 BD-I and BD-II patients were followed using life-chart methodology. Prospective information on SAs of 177 patients (92.7%) during different illness phases was available up to five years. Incidence of SAs and their predictors were investigated using logistic and Poisson regression models. Analyses of risk factors for SAs occurring during MDEs were conducted using two-level random-intercept logistic regression models.

During the five-year follow-up, 90 SAs per 718 patient-years occurred. Compared with euthymia the incidence was highest, over 120-fold, during mixed states (765/1000 person-years [95% confidence interval (CI) 461–1269]) and also very high in MDEs, almost 60-fold (354/1000 [95%CI 277–451]). For risk of SAs during MDEs, the duration of MDEs, severity of depression and cluster C personality disorders were significant predictors.

In this long-term study, the highest incidences of SAs occurred in mixed phases and MDEs. The variations in incidence rates between euthymia and illness phases were remarkably large, suggesting that the question “when” rather than “who” may be more relevant for suicide risk in BD. However, risk during MDEs is likely also influenced by personality factors.

The authors have not supplied their declaration of competing interest.