To examine the statistical significance of this difference, we also estimated a GxE GCTA model, which is shown in the final column of Table 2. The GxE parameter estimate (4.50) is marginally significant (t = 1.70, one-tailed p value = .047) and provides some further support for the social push GxE perspective. The heritability estimate for the full sample is the sum of the genetic and GxE components, and it allows one to consider the contribution of GxE to overall heritability. In this case, 28 % of the additive genetic influences (.28 = 4.50 / (4.50 + 11.69)) on BMI are due to GxE processes. Finally, as with the GWGEI models, we also estimated a comparable GCTA GxE model in which we randomly assigned environmental status, and the model produced a heritability of .52 and a GxE estimate of 0 (SE = 2.22). These results do not necessarily imply that the environment causes genes to operate differently; rather, it simply changes the relative importance of genes vis-à-vis the environment. However, the lack of significance of the GxE component with the
