Duration of euthymia and predominant polarity in bipolar disorder.

Background: The concept of Predominant Polarity (PP) provides relevant information for clinical practice and has been widely described as course specifier for Bipolar Disorder (BD), however it has not been incorporated in DSM-5 yet. A descriptive study was conducted to identify clinical patterns associated with PP in outpatients attending a Mental Health Unit.

Methods: Clinical and socio-demographic characteristics were assessed from a sample of 118 euthymic outpatients fulfilling DSM 5 criteria for BDI or II recruited at a catchment area. According to their PP, patients were divided into three subgroups: depressive (DPP; 39.0%), manic (MPP; 32.2%) or indeterminate (IPP; 28.8%). Subgroups of PP were compared regarding a comprehensive set of demographic and clinical features.

Results: PP subgroups significantly differed in duration of euthymia, measured in months since the last episode (p < 0.04), with MMP patients showing longer periods (42.4 months) than those with DPP and IPP (18.6 and 18.1 months, respectively). Moreover, history of seasonal pattern was significantly higher in the DPP group compared with the PPM group (p < 0.001). There were no significant correlations between PP and type of last episode, length of illness, number of previous admissions, history of psychotic symptoms, or number of suicide attempts.

Limitations: Cross sectional design, relatively modest sample size.

Conclusions: Our study showed similar results to previous literature regarding distribution of predominant polarity. The association found between PP and duration of euthymia represents a novel finding which awaits confirmation and adds further support to the usefulness of PP in clinical practice.