In a study of 50 manic probands we observed 14 (28%) who had never suffered a depressive episode, and compared these unipolar manics with the remaining bipolar manic-depressives for phenomenologic, demographic, genetic, and treatment response variables.
We found no differences between the unipolar and bipolar groups for the clinical psychopathology of the index admission, most of the relevant demographic variables, or the response to "doctor's choice" treatment. The bipolar patients were younger at illness onset and had a greater genetic loading for affective illness and alcoholism, but these differences disappeared when all early onset probands (onset <30 yr) were excluded from analysis.
We conclude that unipolar mania is clinically homogeneous with bipolar, manic-depressive illness, without identifying phenomenologic or treatment response features, and that it is the age at first onset of affective illness that is useful for separating manic probands into diagnostic groups.
Abrams R, Taylor MA. Unipolar ManiaA Preliminary Report. Arch Gen Psychiatry. 1974;30(4):441-443. doi:10.1001/archpsyc.1974.01760100015003