Suicide mortality and use of psychotropic drugs in patients hospitalized due to bipolar disorder: A Finnish nationwide cohort study

Background: Knowledge on the comparative effectiveness of pharmacological treatments to prevent suicide mortality in bipolar disorder is still lacking. Methods: We studied the risk of suicide mortality during 1996-2012 among all patients who had been hospitalized due to bipolar disorder in Finland (n = 18,018; mean follow-up time 7.2 years) using nation-wide databases. We used a Cox proportional hazards model. Analyses were adjusted for the effects of time since diagnosis, order of treatments, current use of other treatments, polypharmacy, number of suicidal hospitalizations within 2 year (indicator of inherent risk of relapse), age at index date, sex, and calendar year of index date. In secondary analysis, the first 30 days were omitted from analysis after initiation of a psychopharmacological treatment to control for protopathic bias. Results: In comparison between use and no use among specific agents, only lithium (HR 0.33, 95%CI 0.24-0.47, p<0.0001) and valproic acid (HR 0.61, 95%CI 0.48-0.79, p=0.0002) were associated with a significantly decreased risk of suicide in bipolar disorder. Lithium showed a 42% lower risk for suicide mortality compared to valproic acid (HR 0.58, 95% CI 0.39-0.86, p=0.007). Hypnotics were associated with a significantly (HR 1.52, 95%CI 1.22-1.90, p=0.0002) higher risk of suicide. Limitations: Only hospitalized patients were included. Conclusions: Lithium should be considered as treatment of choice for patients with bipolar disorder who are at high risk for suicide. Hypnotic use among suicidal patients indicates need for close monitoring of these patients.