As npart of the National Institute of Mental Health Collaborative Study of the Psychobiology of Depression, the comparative course of manic depressive (bipolar) and primary unipolar patients was assessed.
Systematic evaluation using structured instruments every 6 months for a period of 5 years with the recording of remissions, new episodes, and subsequent hospitalizations.
The number of subjects varied somewhat depending on the analyses conducted. For a comparison of course in bipolar patients and unipolar patients, 148 bipolars were compared with 172 unipolar patients.
Both unipolar and bipolar patients were more likely to have episodes if they had episodes prior to index admission. Likewise, prior hospitalizations predicted multiple hospitalizations in follow-up. Chronicity was significantly more prevalent among unipolar depressives but in both unipolar and bipolar patients, chronicity diminished over time. Bipolar patients were more likely than unipolar patients to have multiple episodes at the 2-year and 5-year follow-ups. In bipolar patients, there was no difference in the number of episodes in follow-up between males and females but in unipolar patients, females were significantly more likely to have subsequent hospitalizations and episodes than males. Treatment variables did not relate to these differences. A family history of mania or schizoaffective mania predicted multiple episodes in bipolar patients but not in primary unipolar depressives. A family history of all affective illness (mania, schizoaffective mania, bipolar II illness, and depression) did not predict a multiple-episode course in either bipolar or unipolar illness. In unipolar patients, the independent variables leading to multiple-episode course in follow-up are being female, an early age of onset, and prior episodes.
As a result of this systematic follow-up study, new data add to the distinction between bipolar and primary unipolar patients both as regards number of episodes in follow-up and also as regards risk factors that are associated with the multiple-episode course.