Genetic tests as prophecy: understanding self-defeating and self-fulfilling mechanisms in (predictive) genetic testing.

Predictive genetic tests are reflexive in that they have the potential not merely to indicate plausible future health outcomes, but to influence the eventual outcome. This article offers an overview of how genetic tests can be self-fulfilling, self-defeating, or otherwise influence what happens to the person's health. Certain reflexivity is in fact the primary goal of testing, as when those at risk of inherited cancers intend to use this knowledge to decrease said risk. Our analysis emphasises unintended, poorly understood, and often overlooked, reflexive effects of predictive genetic testing, as these may become increasingly important in genetic counselling. First, there is reflexivity in predictive testing for Mendelian, 'monogenic' disorders. Second, other reflexive mechanisms reveal the potential for feedback loops between genetic susceptibility and expectations held by the self or others-which are even greater, and more complex, in the context of polygenic susceptibility tests for psychiatric illness and cognitive and behavioural traits. Finally, there are additional implications if these tests are used in prenatal genetic testing. These reflexive effects are increasingly likely as genomic testing is more broadly applied to complex diseases and encouraged by trends in personalised medicine-and especially with direct-to-consumer, commercial genetic testing remaining largely unregulated. Recognising the scope of reflexive predictive effects is already useful in genetic consultation and will become more important as the scope of genomic testing broadens to more complex diseases and non-disease traits. Understanding the underlying mechanisms will furthermore increase the possibility of consciously choosing a beneficial response or effective treatment. Without attention to these effects, the consequences of tests for susceptibility to more complex traits are likely to remain opaque and therefore difficult to evaluate and regulate.