Rüdin developed the concept of "empirical genetic prognosis" of mental disorders. He published influential initial results on the genetics of schizophrenia (known as dementia praecox) in 1916. Rüdin's data did not show a high enough risk in siblings for schizophrenia to be due to a simple recessive gene as he and Kraepelin thought, but he put forward a two-recessive-gene theory to try to account for this. This has been attributed to a "mistaken belief" that just one or a small number of gene variations caused such conditions. Similarly his own large study on Mood disorders correctly disproved his own theory of simple Mendelian inheritance and also showed environmental causes, but Rüdin simply neglected to publish and continued to advance his eugenic theories. Nevertheless, Rüdin pioneered and refined complex techniques for conducting studies of inheritance, was widely cited in the international literature for decades, and is still regarded as "the father of psychiatric genetics".