Critique of the Danish-American studies of the biological and adoptive relatives of adoptees who became schizophrenic.

The authors present various reasons why their analysis of the data provided by the Danish-American studies of the relatives of adoptees who became schizophrenic demonstrates that the data do not support the investigators' claims that their studies provide conclusive evidence of a significant genetic factor in the etiology of schizophrenia. When taken together with the authors' earlier demonstration that the investigators' more direct study of the adopted-away offspring of schizophrenic parents failed to provide statistically significant evidence of a genetic influence, these adoption studies indicate that although genetic factors may play some role in the etiology of chronic schizophrenic disorders, such findings are far from definite or proven.