PHILADELPHIA PSYCHIATRIC SOCIETY

Abstract

The scientifically unproductive nature-nurture controversy in relation to disorders of human behavior, particularly schizophrenia and the manic-depressive psychosis, will cease as soon as it becomes generally accepted that an understanding of the principles of human genetics is indispensable for many diagnostic, therapeutic and preventive purposes of psychiatry. The need and feasibility of a consistent system of diagnostic classification with respect to schizophrenic, manic-depressive and involutional psychoses are indicated by a comparative analysis of the taint distribution observed in a total of 6,115 blood relatives (parents, siblings and co-twins) of statistically representative samples of psychotic twin index cases (1,232 twin index families). There is no evidence supporting either the popular hypothesis of a genetic relation between the entities of schizophrenia and manic-depressive psychosis (in the sense of interchangeable or somehow complementary genie elements of causation) or their pessimistic relegation to the status of semantic conventions. It is safe to assume that the mode of inheritance is that of a single recessive in schizophrenia and an irregularly dominant in manicdepressive psychosis. The principal genetic affinity of involutional psychosis is to the group of schizoid personality traits, and therefore at least indirectly to the schizophrenic disease entity, rather than to that of the manic-depressive psychosis.