-Weaver et al: Yes, it could be. There is evidence, I believe, about infant bonding during the first year that shows a near “all or nothing” effect on stress response and neural pathways. The analogous behaviors in humans would be swaddling and holding. Case series of children who lived in orphanages or group homes during the first year of their lives, where human contact and holding were limited have shown that this period may in fact be critical. If they are deprived, but then receive this care later, the effects are not undone.
-Provide a brief proposal for a study: Using substance abuse as an outcome, subjects who resided in orphanages or group homes during the first two years of their lives could be compared to subjects who were in such orphanages or group homes but were adopted by age 3 months. The hypothesis being that those deprived of regular contact during this formative time would have dysfunctional stress response leading to more additive behaviors. If we assume the relevant epigenetic changes are tissue specific and occur in the brain, we could use MRI to look for tissue differences such as differences in size of amygdala or frontal cortex.
-Gruenewald, in contrast to Weaver: The Gruenewald article are somewhat consistent with the Weaver article. The Gruenewald articles describes the effects of socioeconomic adversity over the life course, but emphasizes the impact on childhood. This is similar to the Weaver article which focuses on the epigenetic changes seen in criticl time period in what would be childhood for the rats. However, the Gruenewald article does show evidence that the effect over the lifetime is also important. Those who were downwardly mobile in SES from childhood to adulthood show similar if not worse than those who had adverse SES as children. This differs from Weaver, in that it shows that while childhood is important, it is not the critical period as seen in Weaver.
- 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?
This, I think, varies by the outcome of interest, though it does seem reasonable that this theory could be contributory to disparities along racial or SES differences. The authors use the example of low-MAOA activity allele in association with childhood maltreatment, and how it is associated with criminal activity. The stressors associated with systemic racism or poverty could be associated with environmental factors that might increase the risk of activation of the gene in question.