Depression subtypes in bipolar I and II disorders

Depression is the predominant mood alteration in bipolar I and II disorders. In this study, the nature of major depressive episodes of bipolar I versus bipolar II patients is specifically assessed, as regards lifetime history of rapid cycling, melancholia, atypical and psychotic symptoms.

The patient sample consisted of 184 bipolar I and 80 bipolar II patients, according to the research diagnostic criteria, who entered the bipolar disorders program in our hospital. Subsets of patients are compared according to DSM-IV criteria for rapid cycling, melancholic, atypical and psychotic features.

Bipolar I patients had significantly more psychotic symptoms in their lifetime histories (p < 0.001), whereas bipolar II patients had significantly more atypical symptoms in their lifetime histories (p < 0.003). Although melancholia was more prevalent in the bipolar I and rapid cycling was more prevalent in the bipolar II subgroup, these differences did not reach statistical significance.

The results of the study suggest that marked differences exist in the nature of major depressive episodes between bipolar I and II patients, as they in the long term emerge from the two conditions. To what extent both conditions are related cannot be ascertained in the present study. Clinical differences may have relevant therapeutic implications and separate trials for bipolar I and bipolar II depression are warranted.