Mood-stabilizing pharmacological treatment in bipolar disorders and risk of suicide

Objectives: This study investigated the association between continued mood-stabilizing treatment (lithium and anticonvulsants) in bipolar disorder (BD) and the risk of suicide. Methods: Using linkage of national registers, the association between continued mood-stabilizing treatment and suicide was investigated among all patients discharged nationwide from hospital psychiatry as an in- or outpatient in a period from 1995 to 2000 in Denmark with a diagnosis of BD. Results: A total of 5,926 patients were included in the study and among these 51 patients committed suicide eventually during the study period. Although the rate of suicide was higher during periods when patients purchased anticonvulsants (293 suicides per 100,000 person-years) than during periods with lithium (136 suicides per 100,000 person-years), the suicide rate decreased with the number of prescriptions in a rather similar way for patients first treated with lithium and patients first treated with anticonvulsants: patients who continued treatment with mood-stabilizing drugs had a decreased rate of suicide compared to patients who purchased mood stabilizers once only [rate ratio for anticonvulsants = 0.28, 95% confidence interval (CI) = 0.19-0.41; rate ratio for lithium = 0.20, 95% CI = 0.10-0.38]. Further, the rate of suicide decreased consistently with the number of additional prescriptions. Switch to or augmentation with lithium to patients initiated on anticonvulsants was associated with a significantly reduced rate of suicide (rate ratio = 0.28, 95% CI = 0.20-0.40), whereas a switch to or augmentation with anticonvulsants to patients first started on lithium showed no additional effect on the suicide rate. Conclusions: Although continued treatment with anticonvulsants and continued treatment with lithium was associated with a rather similar reduction in the rate of suicide, the results suggest that treatment with lithium may have some superiority in relation to prevention of suicide.