Bipolar II versus unipolar chronic depression: a 312-case study

Differences between bipolar II depression and unipolar depression have been reported, such as a lower age at onset and more atypical features in bipolar II depression. The aim of the present study was to compare chronic/nonchronic bipolar II depression with chronic/nonchronic unipolar depression to determine whether the reported differences are present when chronicity is taken into account. Three hundred twelve outpatients in a bipolar II/unipolar major depressive episode were assessed with the Structured Clinical Interview for DSM-IV-Clinician Version (SCID-CV), the Montgomery and Asberg Depression Rating Scale (MADRS), and the Global Assessment of Functioning (GAF) Scale. No significant difference was found between chronic bipolar II and chronic unipolar depression (age at intake and onset, gender, duration of illness, recurrences, psychosis, atypical features, axis I comorbidity, and severity). A significantly lower age at onset and more atypical features were observed when comparing chronic/nonchronic bipolar II with nonchronic unipolar depression. These findings suggest that differences reported between bipolar II and unipolar depression are mainly due to nonchronic unipolar depression. Chronic unipolar depression may be a subtype intermediate between bipolar II depression and nonchronic unipolar depression.