Dementia praecox and manic-depressive insanity in 1908: a Grade of Membership analysis of the Kraepelinian dichotomy.

Grade of Membership (GoM) analysis, a multivariate classification technique based on fuzzy-set mathematics, was applied to the demographic, history, and mental-state data on 53 dementia praecox cases and 134 manic-depressive insanity cases admitted to Kraepelin's University Psychiatric Clinic in Munich in 1908. The original data recorded by Kraepelin and his collaborators on special Zählkarten (counting cards) were rated and coded in terms of the Present State Examination (PSE) Syndrome Check List. The statistical analysis resulted in a high degree of replication of Kraepelin's clinical entities. However, the dichotomy of dementia praecox and manic-depressive insanity was not fully supported. The catatonic syndrome tended to occupy an intermediate position between the two major psychoses. The possibility is discussed that catatonia in Kraepelin's time shared certain clinical features with the later diagnostic groupings of schizoaffective disorder, cycloid psychoses, and other "atypical" forms of psychotic illnesses.