Bipolar disorder: are there manic-prone and depressive-prone forms?

Descriptive studies from the prelithium era and lithium prophylactic studies were reviewed to look for evidence that there are manic-prone and depressive-prone subtypes of bipolar illness. The manic-prone subtype has a high ratio of manic to depressive episodes, and a depressive-prone subtype has the reverse. Although data from the prelithium era are suggestive, the evidence is insufficient to accept or reject the relevance of this hypothesis. Data from the lithium era suggest that there is a relationship between the type of index episode and future episode on placebo as well as drug. The clinical and heuristic implications of the relationship of index to subsequent episode and manic proneness and depressive proneness are discussed. Its relevance for planning prophylactic drug studies is also examined. The suggestive evidence presented here will hopefully encourage other investigators to collect the data necessary to test the possibility that manic-prone and depressive-prone subtypes of bipolar illness exist.