Of 39 patients consecutively admitted for the treatment of primary
mania, 21 (53.8%) simultaneously met the Research Diagnostic Criteria for
major depressive disorder ("mixed" or "depressive" mania). Only nine
(42.9%) of the 21 patients with depressive mania responded to antimanic
agents. In contrast, 16 (88.9%) of the 18 patients with pure mania
responded to these drugs. This finding is consistent with previous reports
suggesting that the mixed state is a virulent form of mania.