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 believe this mechanism is relevant in humans and is most analogous to the basic care and nurturing we do babies such as swaddling and holding, particularly in response to crying. I imagine that parental behavior influences stress response beyond just infancy although I really hope it’s not as time sensitive in humans and parents have numerous opportunities to influence their child’s entire life and not just some tiny window of opportunity. But if it is a tiny window, that does explain a lot of people and personalities…
2. Provide a brief proposal for a study that would allow you to assess whether epigenetic modifications in humans in response to maternal behavior influence subsequent health of the human (feel free to choose any health or behavioral outcome you think you can do this with, e.g., dementia or depression or smoking). Bonus if you can explain how you would approach this if we assume that the relevant epigenetic changes are tissue specific and occur in the brain.
I honestly can’t think of any type of study that would test maternal behavior and later health outcomes while controlling for every other external factor that I believe has a greater impact on health than just gene expression. I was thinking of something along the lines of early skin-to-skin in newborns or breastfeeding but even if those maternal behaviors had an epigenetic effect and potentially had some protective effect for a disease later in life, there are so many other environmental and social factors that could be of greater influence on health that proving the epigenetic effect isn’t that important to me. Parenting is hard, most mothers and fathers try their best. Discovering that there is a specific behavior and time in which to perform them lest their child may have some issue later in life doesn’t strike me as the most consequential path to improving health.
3. Gruenewald, in contrast to Weaver, emphasizes 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.
The two studies are similar in the fact that they both show the influence of external factors on health - the Weaver article looked at the epigenomic state of a gene based on external behavior whereas the Gruenewald article was SES on allostatic load measure. However, while Weaver demonstrated that the effect was reversible, Gruenewald doesn’t make that inference, rather the cumulative effect of SES over the life course is what has the most impact on AL.
4. 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?
Based on the two previous articles by Weaver and Gruenewald, it is exactly this interaction of genes and environment that contribute to disparities in health. SES and environmental factors influence health and they can influence gene expression. Together, health disparities along racial/ethnic and SES lines are exacerbated.