Genotype–environment interaction in schizophrenia-spectrum disorder

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Abstract
Background: Earlier adoption studies have convincingly confirmed the importance of a genetic contribution to schizophrenia. The designs, however, did not incorporate observations of the rearing-family environment.Aims: To test the hypothesis that genetic factors moderate susceptibility to environmentally mediated risks associated with rearing-family functioning.Method: A Finnish national sample of adopted-away offspring of mothers with schizophrenia-spectrum disorders was compared blindly with adoptees without this genetic risk. Adoptive rearing was assessed using family rating scales based upon extended family observations at initial assessment. Adoptees were independently re-diagnosed after a median interval of 12 years, with register follow-up after 21 years.Results: In adoptees at high genetic risk of schizophrenia, but not in those at low genetic risk, adoptive-family ratings were a significant predictor of schizophrenia-spectrum disorders in adoptees at long-term follow-up.Conclusions: Adoptees at high genetic risk are significantly more sensitive to adverse v. ‘healthy’ rearing patterns in adoptive families than are adoptees at low genetic risk.