SOME FACTORS ASSOCIATED WITH CONCORDANCE AND DISCORDANCE WITH RESPECT TO SCHIZOPHRENIA IN MONOZYGOTIC TWINS

Abstract

This study is concerned with biological unity in schizophrenia. The case histories on monozygotic twins published by Slater (20) are analyzed with respect to 3 hypotheses. There is almost a total absence of schizophrenia in the families of the discordant twin pairs, but the illness occurs in about 60% of the families of the concordant twin pairs. Affected discordant male twins tend to have a later age of onset and more favorable outcome than concordant male twins. The former tend to be of paranoid subtype; the latter catatonic. Of the discordant male twins, the one who does not become ill tends to have the better premorbid social and sexual history, and the twin who does become ill tends to have a better premorbid adjustment than do concordant twins. Biologically speaking, at least 2 broad groups of schizophrenia are differentiated by this method of analysis: in one, the genetic contribution is absent or minimal; in the other, the genetic contribution is probably considerable.