Lithium response and the sequence of episode polarities: preliminary report on a Hamilton sample

This is a preliminary report on a study which replicated the finding of a significant relationship between the response to long-term lithium stabilization and the sequence of episode polarities (depressive/manic) in bipolar and schizoaffective (bipolar) patients. The lithium response and the clinical course data were assessed independently, in a blind manner, utilizing a data collection which has been gathered in earlier studies. There was a significant association between lithium response (stability achieved on long-term lithium treatment) and the sequence of episode polarities. The main determinant of this association was a close link between lithium response and the MDI sequence of episode polarities. The observed association may be explained in several ways: as an artifact; due to the exclusively antimanic effect of lithium; due to true psychobiological differences between mania and depression; as a result of the differences between bipolar type one and type two patients; and finally due to bipolar heterogeneity. Considering the data available to date the explanation via bipolar heterogeneity appears to be the most likely one.