Abstract

Between Theory and Interpretation of the Hereditary Transmission Process of Mental Disease. The Introduction of Mendelism in German and North American Psychiatry, 1911–19301911 saw the beginning of decisive developments in psychiatric genetic research. During that year, two expert papers dealing with the application of the Mendelian Theory were published in Germany and in the United States. Only a decade after the “rediscovery” of the Mendelian Laws simultaneous efforts were being made to better understand the hereditary transmission process of mental diseases by means of the Mendelian Theory. The results of these efforts were disparate. While in the United States, the Mendelian theory was used to support the polymorphous theory of the hereditary transmission process of mental diseases, by which a common hereditary origin of mental diseases was assumed, the introduction of Mendelism in psychiatry in Germany focused on corroborating Emil Kraepelin’s concept of a disease entity. The Mendelian Theory especially helps to underpin the idea of a specific genetic origin of the clinical diseases described by Kraepelin. As German and North American psychiatric genetics were inspired by diverse disease and genetic concepts, so too was their use of the Mendelian Theory very divergent. Research linked to the use of the Mendelian Theory was both dissimilar and hotly contested. This was due to the fact that it was difficult, if not impossible to identify Mendelian patterns by studying the hereditary transmission process. As a result, the approach of studying the genetic basis of mental diseases was further developed in Germany.