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 think the mechanism described by Weaver et al is relevant to humans. In particular, I think a behavior in humans that is analogous to maternal licking and grooming is holding/playing with a newborn. These behaviors are important interactions between a mother and child, and would likely have an impact on a newborn’s connection with his/her mother and social interactions later in life. It is possible that if a mother does not engage with her child frequently, the child might be socially detached and more stressed. This maternal behavior during this critical period of development is important for a newborn to begin having social interactions and connection with his/her mother.
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 that the Gruenewald findings are not entirely consistent with the Weaver findings. The notion of lifecourse SES adversity leading to an increased allostatic load focuses on a myriad of external factors that have long-term physiological implications on an individual. The Weaver findings focus on critical events during infancy, and how they can impact genetic traits. Furthermore, Weaver’s findings focus on very specific actions and behaviors that could impact a pup in a very sensitive period of development, while Gruenewald’s findings focus on events during the lifecourse, potentially at several different sensitive periods of development. Gruenewald found higher levels of allostatic load in middle and later adulthood individuals who experienced SES adversity throughout the lifecourse, from childhood to adulthood. In Weaver’s work, behaviors such as grooming and licking seem to have a profound impact on stress responses in pups. While the findings from the studies touch on how different factors can influence individuals throughout their life, there is a difference in the duration of effect and what impact, physiological versus genetic, it may have on an individual.
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?
I think gene x environment interactions can contribute to major disparities across several dimensions. I think the environment affects individuals throughout their life, and it would not be surprising at all if this had biological implications. This is particularly salient with chronic diseases such as diabetes, where different environmental and social behaviors throughout life could have a profound impact on who is more predisposed to developing diabetes. The Hertzmann and Boyce paper outlines several potential experiences and influences from infancy through adulthood that could impact biological or physiological attributes. However, the research seems to indicate that children are at the greatest biological risk because there are more critical periods of development at a younger age. This finding would support that gene x environment interactions play a major role in disparities, since the effects would potentially be ingrained in an individual at a very early age. While there is currently not a lot of research into this area, I think it is an important topic that could have profound implications on disparities of racial/ethnic, socioeconomic, or geographic dimensions.