The place of Franz Kallmann's 1938 “the genetics of schizophrenia” in the history of psychiatric genetics

This essay provides the historical context and key findings of one of the largest fieldwork-based family studies ever done in the history of psychiatric genetics conducted in Berlin by Franz Kallmann from 1929 to 1933. It included over 1,000 schizophrenic probands and 12,500 of their relatives including siblings, offspring, nieces/nephews and grandchildren. The work was analyzed in close collaboration with Rüdin, Schulz, and Luxenburger in Munich. Born of Jewish parents, Kallmann had to leave Germany in 1936, completing and publishing the monograph in the United States in 1938. This study included a number of methodologic advances over the classic 1916 sibling study of Rüdin: (a) joint analysis of multiple classes of relatives; (b) subdivision of schizophrenia into four subtypes; (c) a focus on schizoid personality [schizoidia]; (d) examination of the familial aggregation of schizophrenia; and (e) a more complex genetic model—with schizophrenia arising from a single-recessive gene with 70% penetrance and background polygenic influences, and schizoidia from heterozygotes. Kallmann found important differences in risk of relatives in nuclear versus peripheral subtypes and concluded that schizoidia was a part of schizophrenia disease complex while other psychopathies, feeblemindedness, and organic brain disorders were not. Kallmann was strongly invested in the eugenic implications of his results.