The conflict of the nosologists: views on schizophrenia and manic-depressive illness in the early part of the 20th century.

The distinction between schizophrenia (dementia praecox) and bipolar disorder (manic-depressive insanity), proposed by Kraepelin in 1896, was the subject of vigorous debate in the first decades of this century. The debate addressed fundamental questions about the principles underlying the nosology of psychiatric disorders, and the issues raised remain as relevant today as at the time they were formulated. A meta-analysis of a sample of Kraepelin's primary data suggests that his original classification was consistent with the empirical evidence. However, heeding his critics, Kraepelin modified considerably his earlier views and proposed a conceptual model of the pathogenesis of schizophrenia and affective psychosis that is consonant with present-day ideas arising out of neuroscience and genetics. The lesson to be drawn is that nosological arguments should be put on hold until basic understanding is gained of the specific mechanisms of syndromogenesis across diagnostic boundaries.