Interaction of genetic and psychosocial factors in schizophrenia.

What the genetic and family dynamic theory have in common, is that the cause of schizophrenia could be found in the family. Usually the genetic factors and the rearing factors are confounded in the same family. In a study of adoptive children given away for adoption early enough, discrimination between these two sets of factors is possible. A nation-wide sample of offspring of schizophrenic mothers, given away for adoption, has been compared blindly with matched controls, i.e., adopted-away offspring of non-schizophrenic biologic parents. The families have been investigated thoroughly with joint and individual interviews and psychological tests. In the 91 pairs where both the index and control families have been investigated and rated so far, the total number of severe diagnoses (psychosis, borderline, character disorder) is 28.6% (26/91) in the index group and 16.5% (15/91) in the matched control group. Of the 7 psychotic cases, 6 are offspring of schizophrenics and only one a control offspring. The relation of psychopathology of adoptive families to the mental health ratings of the offspring supports the hypothesis that a possible genetic vulnerability has interacted with the adoptive rearing environment.