1. Weaver et al propose that among rats, maternal behavior towards newborn pups influences their cortisol response to stress via epigenetic mechanisms that change the expression of glucocorticoid receptor gene for the rest of the pup’s life. They argue that because epigenetic patterns are established at specific developmental periods, there is extreme time sensitivity to when the pup is exposed to particular maternal behaviors (licking and grooming, in this case), and maternal behavior before or after that sensitive period window is not as important. Do you think this mechanism is relevant in humans? If so, what behaviors are most analogous to “maternal licking and grooming”?
I do believe this is relevant to humans, however because of the way that we have somewhat “proceduralized” the labor and delivery experience here in the United States as well as have lower breastfeeding rates compared to other countries, this may not seem immediately relevant within our culture. Analogous behaviors would be initiation of immediate skin-to-skin contact between mother and newborn right after delivery, attempt to initiate breastfeeding within the 1st hour of delivery, encouraging exclusive breastfeeding/pumping through at least the first 6 months of life and “rooming in” where the healthy newborn (not in need of intensive care) stays in the mothers room during the postpartum hospitalization and can be extended into home life. These behaviors could definitely have an effect on these epigenetic mechanisms, and I think that hospital policies around the country are attempting to encourage and implement these positive and immediate maternal-newborn interactions perhaps in response to literature such as this and others. It is plausible that these important early interactions during this sensitive time frame potentially build some “resiliency” in the child for the rest of their life when other insults occur, however I do think there are probably exceptions to this sensitive time period in cases of extreme trauma later in childhood that can play a significant developmental role as well.
2. Gruenewald, in contrast, emphasize the cumulative effects of SES adversity on a multi-system allostatic load measure. Do you think that the Gruenewald findings are consistent, inconsistent, or unrelated to the Weaver findings? Explain.
I think these two papers complement each other, with Weaver’s paper detailing the importance of early biologic and genetic effects from maternal-newborn interaction and Gruenewald’s paper emphasizing that persistence or accumulation of additional SES insults/adversity can affect developmental and health outcomes. I think there is interplay between these two findings that contribute to the broader picture.
3. Hertzmann and Boyce argue that “it is not genes or environment, nor is it genes and environment, but rather it is gene-by-environment interactions that influence developmental trajectories.” To what extent do you think that GxE interactions can contribute to major disparities along racial/ethnic, socioeconomic, or geographic dimensions?
If certain maternal-newborn interactions and behaviors are influenced by the surrounding environment and various SES factors, and through these influences epigenetic mechanisms change gene expression that then gets coded into one’s DNA which then gets passed down to their offspring, this could initiate a cycle that is only potentiated by propagation of these genes within a family or ethnic group and further augmented by environment. This would result in clustering of these altered genetic mechanisms that are then affected by the clustering of certain types of environmental exposures along racial/ethnic, socioeconomic or geographic dimensions that would create a sort of snowball effect in these developmental trajectories.