The author reviews the results of twin studies of schizophrenia from the
perspective of recent advances in our understanding of the twin method and
of the transmission of schizophrenia. The evidence suggests that twin
studies of schizophrenia are not likely to be substantially biased by the
greater similarity in social environment of identical versus fraternal
twins. Raw concordance figures from twin studies of schizophrenia are quite
variable. When models to estimate the etiologic importance of genetic
factors are applied to these figures, the results from all studies are
similar. According to these models, genetic factors are as etiologically
important in schizophrenia as in such medical conditions as diabetes and
hypertension. Twin studies of schizophrenia probably provide a valid
measure of the major etiologic role genetic factors play in
schizophrenia.Abstract Teaser