[Twin studies with a differentiated diagnosis of endogenic psychoses - psychosocial influences in certain forms of schizophrenia].

The examination started from the premise that "systematic schizophrenias", which constitute the majority of chronic schizophrenias in "differentiated diagnostics", only very rarely have a family history of psychosis. We set out to obtain an explanation of this observation by means of investigation in twins. Surprisingly, these types were not present in identical twins. It seems, therefore, that the severe schizophrenias, which we consider to be similar in character to systemic diseases, are prevented by the influence of an identical twin partner. As, however, the illness did occur in two-egg twins, the favourable influence must be effective during a period of life, when mutual understanding between the twins is already decisive, i.e. during later childhood, probably during puberty. An interaction between individual and environment is probably necessary for normal mental development and also for the maturing of brain systems essential in the adult psyche. In autistic patients there is no interaction, thus schizophrenia may develop. With an identical twin, however, contact is always present: because of similarity in character it is impossible that the partners minds are not mutually accessible. Thus, a satisfactory mental interrelationship is maintained, by which systematic schizophrenia is prevented. For refernces see the end of the following communication.