Thanks for these comments Carlo. What would it mean for GxE interactions to be mediated by heritable genetic changes?
An important aspect of the Weaver et al work, and in general about epigenetic modifications, is that they are changes that regulate gene expression, not genetic code. These are changes to how the DNA is packaged that make it more difficult for the polymerase to get in and transcribe into RNA, but those differences in packaging are not necessarily passed along to the next generation (although in some cases they are, it's just a little unclear at this point how persistent epigenetic modifications are).
I love the link you are making between psychological development and biological processes that may underlie those psychological processes. This is the point of today's class really: can we open the hood and look at physiologic pathways that can explain what we observe in health inequalities, in health behaviors, at a macro level?