The examination of Kraepelin's diagnoses of dementia praecox and manic-depressive insanity in pedigrees: Studies of Schuppius in 1912 and Wittermann in 1913.

In the first two decades of the 20th century, a new approach to psychiatric genetics research emerged in Germany from three roots: (i) the wide-spread acceptance of Kraepelin's diagnostic system, (ii) increasing interest in pedigree research, and (iii) excitement about Mendelian models. We review two relevant papers, reporting analyses of, respectively, 62 and 81 pedigrees: S. Schuppius in 1912 and E. Wittermann in 1913. While most prior asylum based studies only reported a patient's "hereditary burden," they examined diagnoses of individual relatives at a particular place in a pedigree. Both authors focused on the segregation of dementia praecox (DP) and manic-depressive insanity (MDI). Schuppius reported that the two disorders frequently co-occurred in his pedigrees while Wittermann found them to be largely independent. Schuppius was skeptical of the feasibility of evaluating Mendelian models in humans. Wittermann, by contrast, with advice from Wilhelm Weinberg, applied algebraic models with proband correction to DP in his sibships with results consistent with autosomal recessive transmission. While he had less data, Wittermann suggested that MDI was likely an autosomal dominant disorder. Both authors were interested in other disorders or traits appearing in pedigrees dense with DP (e.g., idiocy) or MDI (e.g., highly excitable individuals).