LONG-TERM STABILITY OF POLARITY DISTINCTIONS IN THE AFFECTIVE-DISORDERS

Objective: This analysis aimed to quantify the long-term stability of distinctions between nonbipolar, bipolar II, and bipolar I affective d isorders and to determine the predictors of shifts in patients' diagno ses among these categories. Method: Probands entered the study as they sought treatment for manic, major depressive, or schizoaffective diso rder diagnosed according to the Research Diagnostic Criteria. After th orough baseline evaluations, 605 patients with nonbipolar major depres sive disorder or schizoaffective disorder, depressed type; 96 with bip olar II disorder; and 231 with bipolar I disorder or schizoaffective d isorder, manic type, began the follow-up study. Direct interviews took place at 6-month intervals for the first 5 years and annually thereaf ter. Results: Only 20 (5.2%) of the 381 initially nonbipolar probands who completed 10 years of follow-up developed mania during that time, and only 19 (5.0%) developed hypomania. A slightly higher proportion o f the 67 who began with bipolar II disorder developed mania during the 10 years. Although 101 (66.4%) of the 152 bipolar I or schizoaffectiv e manic probands developed subsequent manic episodes, only 11 (7.2%) d eveloped hypomanic episodes and no mania. Young age at intake and at o nset and chronicity of the index episode predicted shifts from nonbipo lar to bipolar II disorder. Psychosis and a family history of mania pr edicted shifts from nonbipolar to bipolar I disorder. Conclusions: The high stability of baseline distinctions between nonbipolar, bipolar I I, and bipolar I disorders, in combination with previously described f amily study data, strongly supports the separation of these disorders for both clinical and research purposes.