Clinical correlates of first-episode polarity in bipolar disorder

To determine the clinical and long-term implications of mood polarity at illness onset.

During a 10-year follow-up prospective study, systematic clinical and outcome data were collected from 300 bipolar I and II patients. The sample was split into 2 groups according to the polarity of the onset episode (depressive onset [DO] vs manic/hypomanic onset [MO]). Clinical features and social functioning were compared between the 2 groups of patients.

In our sample, 67% of the patients experienced a depressive onset. Depressive onset patients were more chronic than MO patients, with a higher number of total episodes and a longer duration of illness. Depressive onset patients experienced a higher number of depressive episodes than MO patients, who in turn had more manic episodes. Depressive onset patients made more suicide attempts, had a later illness onset, were less often hospitalized, and were less likely to develop psychotic symptoms. Depressive onset was more prevalent among bipolar II patients. Bipolar I patients with DO had more axis II comorbidity and were more susceptible to have a history of psychotic symptoms than bipolar II patients with DO.

The polarity at onset is a good predictor of the polarity of subsequent episodes over time. A depressive onset is twice as frequent as MO and carries more chronicity and cyclicity.