The bipolar unipolar dichotomy and the need for a consistent terminology.

A division of the major psychotic affective disorders into a bipolar (true manic-depressive) and unipolar (recurrent depressive or recurrent manic) group represents a clear advance in the classificatory work of affective illness which had been suffering from stagnation. Several investigations have already contributed provocative findings which support the heuristic value of this distinction. However, to be reliable a separation of bipolar from unipolar affective disorders must rely upon clear-cut definitions of the labels to be used in order to avoid inconsistency in terminology hampering the reliability of our findings.