Differences in incidence of suicide attempts during phases of bipolar I and II disorders

Background:  Differences in the incidence of suicide attempts during various phases of bipolar disorder (BD), or the relative importance of static versus time-varying risk factors for overall risk for suicide attempts, are unknown.
Methods:  We investigated the incidence of suicide attempts in different phases of BD as a part of the Jorvi Bipolar Study (JoBS), a naturalistic, prospective, 18-month study representing psychiatric in- and outpatients with DSM-IV BD in three Finnish cities. Life charts were used to classify time spent in follow-up in the different phases of illness among the 81 BD I and 95 BD II patients.
Results:  Compared to the other phases of the illness, the incidence of suicide attempts was 37-fold higher 95% confidence interval (CI) for relative risk (RR): 11.8–120.3] during combined mixed and depressive mixed states, and 18-fold higher (95% CI: 6.5–50.8) during major depressive phases. In Cox's proportional hazards regression models, combined mixed (mixed or depressive mixed) or major depressive phases and prior suicide attempts independently predicted suicide attempts. No other factor significantly modified the risks related to these time-varying risk factors; their population-attributable fraction was 86%.
Conclusions:  The incidence of suicide attempts varies remarkably between illness phases, with mixed and depressive phases involving the highest risk by time. Time spent in high-risk illness phases is likely the major determinant of overall risk for suicide attempts among BD patients. Studies of suicidal behavior should investigate the role of both static and time-varying risk factors in overall risk; clinically, management of mixed and depressive phases may be crucial in reducing risk.