The clinical epidemiology of pure and mixed manic episodes

Introduction: Few large clinical epidemiological studies have been undertak en comparing subjects meeting criteria for mixed and pure states of bipolar disorder. In part, the difficulty comparing these states emanates from con fusion in their diagnostic separation. In the current report, we use a defi nition derived from receiver operating characteristic (ROC) curve analysis as an alternative to the DSM-IIIR/IV definition, and we compare the two sub types of manic episodes. Methods: Three hundred and sixty-six patients meeting DSM-IIIR criteria for bipolar disorder, manic or mixed, were categorized using newly described c riteria for mixed states. The two subtypes were compared on demographic var iables and clinical history variables, using multiple analysis of variance with post hoc univariate F tests. The same analyses were conducted using th e DSM-IIIR-defined subtypes. Results: Using the ROC criteria, 79 subjects (21.6%) were characterized as mixed, in contrast to 51 subjects (13.9%) using DSM-IIIR criteria for bipol ar disorder, mixed. The ROC-defined mixed manic group comprised more Caucas ians and more females. Age of first psychiatric hospitalization was earlier and duration of illness longer in the mixed group. First episodes were unl ikely to be categorized as mixed (<5%). When the DSM-IIIR definition was em ployed, differences were not demonstrated. Conclusions: An earlier age of first psychiatric hospitalization and increa sed duration of illness, as well as a lower frequency of mixed subtype of m anic episode during first hospitalization, are compatible with the view tha t mixed manic episodes occur more frequently later in the course of bipolar disorder. Moreover, differences in race, sex, and clinical histories of su bjects in mixed episodes tend to support the separation of mixed mania as a diagnostic subtype of bipolar disorder.