Statistical power is the probability of detecting a significant result given that the alternative (here, cG×E) hypothesis is true. Statistical power has been a central issue in modern psychiatric genetics, and it is likely that most candidate gene studies have been underpowered (23). Several studies have likewise investigated the statistical power of cG×E studies (24–27) and have concluded that power to detect cG×E interactions is even lower, sometimes much lower, than power to detect genetic or environmental main effects. Low statistical power in a field is problematic, not only because it implies that any true findings are likely to be missed but also because low power increases the proportion of significant “discoveries” in a field that are actually false.
