Background: Despite the high prevalence of bipolar spectrum disorders, most instruments currently available for the assessment of depression do not explore symptoms of 'activation' such as anger, irritability, aggressiveness, hostility, and psychomotor activation.
Methods: Two samples of adults with unipolar depression were studied. They had no comorbid DSM-IV disorder, and they were free from antidepressant drugs. The first sample (n = 380) was assessed with the SVARAD, a validated scale for the rapid assessment of the main psychopathological dimensions. The second sample (n = 143) was assessed with the MMPI-2. Factor analysis was performed on SVARAD items and MMPI-2 clinical scales.
Results: In both samples, we obtained a three-factor solution with factors interpreted as a depressive dimension, an anxious dimension, and an activation dimension. The latter dimension appeared to be clinically relevant in 20-27% of patients.
Limitations: The presence of a comorbid disorder may have been missed in some cases. Also, some bipolar II patients might have been misdiagnosed as unipolar and included in the study. Further, our findings apply only to a selected psychiatric population, and it should be tested whether they generalize to other settings of care and other countries.
Conclusions: Our results suggest that depressive mixed states are not rare even in patients diagnosed as unipolar, and that some unipolar patients might actually be 'pseudounipolar' and belong to the bipolar spectrum. More in general, our findings suggest that some depressed patients have prominent symptoms of activation that can easily go unnoticed using instruments that do not explore such symptoms. Detecting these symptoms has important treatment implications.