ABSTRACT
Since descriptions by Falret (1) and Kraepelin (2), we have recognized bipolar disorder as an illness defined by its changing course. Both described the disorder as a circular one, essentially alternating between the extreme highs and lows of mood. Kraepelin felt it was this circular course, with a return to normalcy, that differentiated this disorder from dementia praecox (i.e., schizophrenia). Work by Post (3) and others suggested that the course of bipolar disorder could worsen with time. It was found that an increasing number of manic episodes lead both to a further increase of future manic episodes and also a decrease in the period of normalcy between episodes. From this observation came the idea that the course of bipolar disorder was subject to a type of ‘‘kindling’’ phenomenon, analogous to that seen in epilepsy. In the 1960s, the work by Leonhard et al. (4) helped distinguish bipolar disorder from unipolar depression, in part due to perceived differences in the courses of the two disorders. Bipolar disorder was thought to occur earlier than unipolar depression and had more episodes over time.
