Predictors for initiation of pharmacological prophylaxis in patients with newly diagnosed bipolar disorder--A nationwide cohort study.

Background: Treatment guidelines state that all patients with bipolar disorder should use pharmacological prophylaxis; however the actual use of prophylactic drugs after bipolar disorder diagnosis is unknown. Our aim was to assess the use of, and predictors for, pharmacoprophylaxis in newly diagnosed bipolar disorder patients.

Methods: Data from three Swedish nationwide registers were obtained. We identified patients aged 18-75 with a first time diagnosis of bipolar disorder between 2006 and 2012 (n=31,770) and reviewed subsequent mood-stabilizer and antipsychotic prescription fills. In multivariable Cox regression models, we studied demographic and illness related factors as predictors of prescription fills after diagnosis.

Results: In total, 72.2% (95% confidence interval [CI] 71.7-72.7%) of the patients filled a prescription of a prophylactic drug within 3 months after diagnosis. Pharmacological prophylaxis was mainly associated with a longer duration of hospitalization at bipolar disorder diagnosis (adjusted hazard ratio [AHR] 2.18; CI 2.02-2.35 for a hospitalization of ≥28 days compared to <7 days) and previous use of any mood-stabilizer or antipsychotic (inpatients: AHR 1.24; CI 1.17-1.31 and outpatients: AHR 1.78; CI 1.73-1.84).

Limitations: We had no information on drug prescriptions that were never filled.

Conclusions: The proportion of newly diagnosed bipolar disorder patients without pharmacological prophylaxis is substantial. Patients who are naïve to mood-stabilizers and antipsychotics and are hospitalized for a brief period at diagnosis are the ones least likely to initiate pharmacoprophylaxis, suggesting that this group deserves attention in order to improve the long term prognosis.