Is bipolar II depression phenotypically distinctive?

Abstract

Objective: We examine the depressive symptom profile of bipolar II disorder patients compared with a comparator (composite) group of those with unipolar depression, with stratification by melancholic and non-melancholic subtypes.

Method: Out-patients (n = 394) attending a specialist depression clinic comprised the sample. Data on severity and prototypic status of depressive symptoms were analysed.

Results: Age-matched analyses revealed minimal differentiation between bipolar II and composite unipolar groups. Stratified analyses suggested that 'bipolar II depression' more closely approximated melancholic depression in terms of psychomotor and cognitive slowing. Severity-based analyses and prototypic symptom patterns yielded differing results, suggesting that definition of bipolar II depression is influenced by rating strategies, and age.

Conclusion: We found limited differentiation of bipolar II depression from unipolar, melancholic and non-melancholic depression. Differences suggested previously may reflect age, gender and severity differences, highlighting the need for appropriately matched groups in defining bipolar II depression.