Ernst Rüdin and the State of Science.

It should be no surprise to the readers of this journal that the intersection of eugenics, psychiatry, and National Socialism in the work of Swiss-born German scientist and physician Ernst Rüdin ended poorly for the victims of his abominable ideas. As one of the primary architects of Nazi eugenics, Rüdin’s impact was felt most immediately in the euthanasia programs that his ideas instigated and he helped design as chair of the Committee for Racial Hygiene and Racial Policy at the Ministry of the Interior in Hitler’s Germany. That committee gave rise to the “Law for the Prevention of Hereditarily Diseased Offspring,” and that law led to between 350,000 and 400,000 German sterilizations during the Nazi rule [1–2]. But as Kösters et al. [1] illustrate in their important paper in this issue of PLOS Genetics, there is more to Rüdin’s story than just his role in and impact on Nazi eugenic programs. Their paper offers new insights into long-standing debates about how to remember Rüdin and what his story can tell us. Foremost, their paper draws our attention to a dark chapter in the history of genetics and examines Rüdin’s role therein. Of particular interest is the way Rüdin, generally credited as the founder of psychiatric genetics, was deeply entangled in eugenic thought and practice and how his eugenic thinking was inseparable from his genetic research. In that research, Rüdin worked to develop methodologies integrating emerging statistical methods with Mendelian genetics to predict how mental illness passed within families. His goal: an “empirical hereditary diagnosis” of mental illness. But Kösters et al. show how eugenics not only shaped Rüdin’s research questions, but shaped the very fabric of his research endeavor. As their paper reveals, fundamental to Rüdin’s work was “to provide scientific evidence that severe mental illness was inherited, thus strengthening the case of eugenic measures.” Rüdin hoped to use genetics in the service of what he ominously called “therapeutic reform.” Second, by showing that Rüdin suppressed his own findings regarding the inheritance of “manic-depressive insanity” because they offered contradictory evidence to his eugenic worldview, Kösters et al. draw our attention to how far Rüdin was willing to let his ideology drive his science and suppress negative findings to that end. The example provided is a study conducted in the early to mid-1920s (even before the rise of the Third Reich but as eugenic ideas were growing in strength in Germany) on the “Inheritance of Manic-Depressive Insanity” that one biographer describes as “probably the most significant of Rüdin’s work.”However, the results from this study did not conform to Rüdin’s worldview, and did not support his idea that he could use hereditary data to predict “the probability that a particular individual would develop an illness.” Rüdin would never publish these findings. Why not? After all, the “Inheritance of ManicDepressive Insanity” was a completed manuscript ready for publication. Kösters et al. believe that Rüdin’s “demands for negative eugenic measures against patients with affective disorders and their families could not be justified on the grounds of the hereditary figures he had