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.