For instance, in 1946 Franz Kallmann published an influential twin study of schizophrenia in this Journal (3). Kallmann was a psychiatrist and the fourth president of the American Society for Human Genetics. Kallmann’s study of 691 twin pairs was the largest in the field for nearly four decades. Reanalysis of these data (4) yielded an estimate of the heritability of schizophrenia (91%) that was higher than more recent national-scale studies (60–65%) (5, 6). Although Kallmann’s speculation that schizophrenia was due to an autosomal recessive mutation has been disproven, the concluding line of his paper remains exceptionally important, that a genetic theory of schizophrenia is “equally compatible with the psychiatric concept that schizophrenia can be prevented as well as cured.”
