Both direct cG×E replications, which use the same statistical model on the same outcome variable, genetic polymorphism, and environmental moderator tested in the original report, and indirect cG×E replications, which replicate some but not all aspects of an original report, exist in the cG×E literature. Indirect replications might sometimes be conducted to help understand the generalizability of an original report (1) and might in other cases be conducted out of necessity because available variables do not match those in the original report. However, it is also possible that in an unknown number of cases, a positive indirect replication was discovered by testing additional hypotheses after a direct replication test was negative. Sullivan (36) showed that when replications in candidate gene association (main effect) studies are defined loosely, the type I error rate can be very high (up to 96% in his simulations). The possibilities for loosely defined, indirect replications are even more extensive in cG×E research than in candidate gene main effect research because of the additional environmental and moderator predictors. Thus, we believe it is important that only direct
