Mental Illness in the Biological and Adoptive Families of Adopted Schizophrenics

Adoption has been used as a means of separating genetic and environmental factors in the transmission of schizophrenia among family members. In the study reported here, a significantly higher than usual prevalence of schizophrenia-related illness was found among the biological relatives of adopted schizophrenics, but not among their adoptive relatives. The findings support a genetic transmission of vulnerability to schizophrenia, but also imply the requirement of nongenetic, environmental factors for the development of clinical schizophrenic illness.