3 - The continuum of psychosis and its genetic basis

Summary

Kraepelin's 1920 doubts about the binary principle

It is remarkable that over a hundred years after its original formulation Kraepelin's binary concept still dominates psychiatric nosology, even though he had apparently abandoned it. In 1920 he wrote:

Perhaps it is also possible to tackle the difficulties which still prevent us from distinguishing reliably between manic depressive insanity and dementia praecox. No experienced psychiatrist will deny that there is an alarmingly large number of cases in which it seems impossible, in spite of the most careful observation, to make a firm diagnosis. Nevertheless it is becoming increasingly clear that we cannot distinguish satisfactorily between these two illnesses, and this brings home the suspicion that our formulation of the problem may be incorrect.

(Kraepelin, 1920.)

The inadequacies of the original concept are easily demonstrated by contemporary operational criteria. Endicott et al. (1982) presented the findings of a study including 46 consecutive admissions to the Psychiatric Institute in New York with a diagnosis of schizophrenia by seven different operational sets of criteria. The variation in numbers was wide. By Taylor and Abrams criteria (1978), the most restrictive, only six cases were allocated a diagnosis of schizophrenia, whereas by the New Haven criteria of Astrachan et al. (1972), the most liberal, 44 cases were so diagnosed, a ratio of more than 7:1.