Bipolar II depression in late life: prevalence and clinical features in 525 depressed outpatients

Late-life bipolar II depression has not been well studied. The aim of the present study was to find the prevalence of late-life (50 years or more) bipolar II depression among unipolar and bipolar depressed outpatients, and to compare it with bipolar II depression in younger patients, looking for differences supporting the subtyping of bipolar II depression according to age at onset.

Consecutive 525 patients presenting for treatment of a major depressive episode were interviewed with the Structured Clinical Interview for DSM-IV, the Montgomery Asberg Depression Rating Scale, and the Global Assessment of Functioning Scale.

Among patients less than 50 years, 53.4% had bipolar II depression. Among patients 50 years or more, 32.9% had bipolar II depression (significant difference). Atypical features were present in 60.9% of bipolar II patients less than 50 years, and in 26.1% of those 50 years or more (significant difference). Bipolar II patients 50 years or more had significantly higher age at onset than those less than 50 years. Bipolar II and unipolar patients 50 years or more were not significantly different, apart from comorbidity. Bipolar II patients less than 50 years had significantly more atypical features than unipolar ones.

Single interviewer, single nonblind assessment, cross-sectional assessment, exclusion of substance abuse and severe personality disorder patients, comorbidity not systematically assessed, modification of DSM-IV duration criterion for hypomania.

Findings suggest that bipolar II depression and atypical features are less common in late life. Differences in age at onset and atypical features support the subtyping of bipolar II depression according to age at onset.