Etiological Implications of Studies of Identical Twins Discordant for Schizophrenia

I should like to share with you our experiences in studying identical twins discordant for schizophrenia, for I believe that these investigations have taught us a number of lessons about the problems inherent in research on schizophrenia. I also feel fairly confident that they have brought us closer to the long-hoped-for day when some answers to the schizophrenia conundrum will be forthcoming. But despite this guarded optimism, I want most to stress in my remarks here the need for conservatism in interpreting data. We, as investigators, must always be aware of the sometimes damaging effects of our own enthusiasm, which can lead us to report results prematurely. Unfortunately, there are many potentially confounding variables which must be accounted for before meaningfulness — not just statistical significance—can be attributed to data derived from the study of schizophrenia. Although those of us involved in the twin studies to be reviewed here are relatively "conservative" investigators, we have nonetheless reported findings which have been either over-interpreted or misinterpreted—usually because we failed to provide the definitive data which might have allowed us to draw firm, rather than tentative, conclusions.