"Manifestations of insanity": Kraepelin's final views on psychiatric nosology in their historical context.

Emil Kraepelin, more than any other individual, has shaped the nature of our psychiatric diagnostic system. Kraepelin published his final contribution to psychiatric nosology as an essay in 1920, which both modified and explicated the conceptual foundation for this approach to diagnosis. This essay was a response to a new generation of psychiatrists, particularly Karl Jaspers, Karl Birnbaum, and Ernst Kretschmer, who each challenged Kraepelin's view that psychiatric disorders represent natural kinds, (i.e., truly distinct entities). They had argued for a structural analysis of psychosis stressing the impact of unique, personal attributes on the causes and clinical presentations of mental diseases. The authors give this text a close reading and conclude that it offers a final nuanced description of Kraepelin's advanced nosologic views and his emerging interest in life history and culture. Kraepelin held fast to his position that psychiatric disorders represented distinct natural kinds, but acknowledged that the distinctions between them were often obscured by personality, life experiences, and/or cultural effects. Kraepelin used several metaphors to illustrate his final views, that of an "organ register" being the most prominent. Psychiatric disorders, he postulated, belong to three registers, each with its own distinct clinical features and putative brain-based mechanisms. Published a century ago, this final synthesis of Kraepelin's views, a capstone to his career, raises central issues about the nature of psychiatric illness and the appropriate goals for psychiatric nosology. They are fertile issues for psychiatric research and practice today.