Julius Wagner von Jauregg, Otto Diem and research methods for assessing the contributions of hereditary burden to mental illness risk: 1902-1906.

After decades of methodological stasis in 19th century psychiatric genetics, when uncontrolled studies reported high rates of hereditary burden in hospitalized patients, Koller completed the first controlled study in 1895. We pick up this narrative 7 years later when the well-known Julius Wagner v. Jauregg published a biting critique of the then current psychiatric genetics' literature. In 1905, partially in response to Wagner v. Jauregg, Otto Diem attempted to replicate and extend Koller's study. Wagner v. Jauregg then wrote a follow-up to his earlier critique in 1906, commenting on Diem's investigation. Themes discussed in this point-counterpoint included the necessity of statistical methods to draw meaningful conclusions about the impact of hereditary burden on mental illness, the required sample size and proper selection of controls, the classes of relatives which should optimally be studied, the problems of obtaining accurate information on familial illnesses, the nature of the disorders in families which contribute to mental illness risk and the common unquestioned dogmatic belief that insanity is very often due to hereditary causes. Both Wagner v. Jauregg and Diem spoke out forcefully against the common assumption that hereditary burden operated in a deterministic fashion and emphasized the need to consider other causes of illness.