Predominant polarity and temperament in bipolar and unipolar affective disorders

Recently, the concept of predominant polarity (two-thirds of episodes belonging to a single pole of the illness) has been introduced to further characterise subtypes of bipolar disorders. This concept has been proven to have diagnostic and therapeutic implications, but little is known on the underlying psychopathology and temperaments. With this study, we aimed to further validate the concept and explore its relationships with temperament.

This study enrolled 143 patients with bipolar or unipolar disorder. We analysed predominant polarity in the sample of bipolar I patients (N=124), focussing on those who showed a clear predominance for one or the other polarity, and distinguishing manic/hypomanic (MP) from depressive polarity (DP), and a unipolar major depression (UP) group (N=19),. We also assessed temperament by means of the Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A).

Over 55% of the bipolar I sample fulfilled predominant polarity criteria, with two-thirds of those meeting criteria for MP and one third for DP. MP and DP were similar in scoring higher than UP on the hyperthymic/cyclothymic scales of the TEMPS-A; the UP group scored higher on the anxious/depressive scales.

Our results show that both bipolar I MP and DP subgroups are temperamentally similar and different from UP. Depression in DP bipolar I patients should be viewed as the overlap of depression on a hyperthymic/cyclothymic temperament. These findings confirm the value of the predominant polarity concept as well as the importance of temperaments to separate bipolar from unipolar disorders.