al. 1990). In a high-risk study of Danish children with schizophrenic mothers and matched controls, institutional rearing was associated with an elevated risk of schizophrenia only among those children with a genetic predisposition (Cannon et al. 1990). When these subjects were further classified on genetic risk as having one or two affected parents, a significant interaction emerged between degree of genetic risk and birth complications in predicting ventricle enlargement: The relationship between obstetric complications and ventricular enlargement was greater in the group of individuals with one affected parent as compared to controls, and greater still in the group of individuals with two affected parents (Cannon et al. 1993). Another study also found that among individuals at high risk for schizophrenia, experiencing obstetric complications was related to an earlier hospitalization (Malaspina et al. 1999).
