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”?
Yes, I think this mechanism is relevant in humans and would surmise that maternal behaviors that help calm infants or children are most analogous. Mothers’ using skin-to-skin contact with their infants to convey a sense of security could potentially affect infants’ stress responses. In older children, hugs, as an affectionate gesture that involves tactile stimulation, may be another example.
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 Gruenewald’s findings can be consistent with Weaver’s findings because Gruenwald’s study focuses on average effects across a group of people, whereas Weaver’s study focuses on effects of exposures in one individual. Gruenwald’s study shows an effect of increased SES adversity on average multi-system allostatic load: in Figure 2, comparing within each “life period” (1 childhood period, 2 adult periods) and across all “life periods”, increased SES adversity was associated with a higher average multi-system allostatic load among the study participants. Weaver’s findings, on the other hand, focus on the effect of timing of SES adversity and its association with multi-system allostatic load within a single a person’s lifecourse: that is, experiencing SES adversity at “sensitive” time periods during a person’s life may prime him/her to develop physical/psychological risk, as compared to experiencing the same SES adversity at other, less critical time periods (the purpose of comparing the different groups of rats was to try to comment on the effect of the maternal licking and grooming within a single rat).
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?
Gene-by-environment interactions play an essential role in creating and perpetuating all of these types of disparities. From a socioeconomic perspective, lower parental education can lead to poor health literacy and lower income, which can reduce the resources that families have to devote to raising children. As Hertzmann and Boyce discuss, adequate sensory stimulation in infants during critical time periods is necessary for both physical and psychosocial development, and failure to provide those stimuli increases risk of developmental delay. Such developmental delays then limit the child’s educational attainment and income potential as an adult later in life, which exacerbates socioeconomic disparities.
GxE interactions also contribute to racial/ethnic disparities in the above situation because racism and discrimination also reduce resources that some families have for raising children, resulting in the subsequent cascade of events described. Then these resulting disparities unfortunately may be used to perpetuate racism (e.g., using the observation that people of race X do not end up as socioeconomically “successful” or physically/psychosocially “healthy” to justify the incorrect conclusion that these disparities are inherent to being of race X).
From a geographic perspective, families who live in poorer neighborhoods are also more likely to be deprived of community resources that might be able to help alleviate the child-rearing disparities described (e.g., daycare or after-school programs that provide appropriate educational/social stimuli while parents are at work). Another example would be community resources that help reduce negative health behaviors like alcohol or drug addiction. These disparities in community resources then exacerbate geographic disparities in health.