Influence of hereditary factors in psychogenic disorders.

As part of a research project, a sample of 50 pairs of twins (21 pairs of identical twins, 16 pairs of nonidentical twins of the same sex, and 13 pairs of male-female twins, n = 100 test persons) was examined between 1963 and 1969 and recently, 20 years later, followed up. The index twins were drawn from among the patients making use of the services of an outpatient clinic; they had been diagnosed as having psychoneurotic, character-neurotic of psychosomatic disorders. The question again looked into was that of nature versus nurture: identical twins displayed significantly higher similarity with regard to both severity of their neuroses and manifestation of neurotic symptoms than did nonidentical twins. The hereditary factor proved to be of greater import for the continuing childhood neuroses than for the subsiding childhood neuroses. Yet a certain hereditary factor effect was observed for the neuroses which first manifest themselves in adulthood. Our findings indicate that the hereditary factor is not more pronounced in childhood than in adulthood; it is equally effective in adults.