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 have read about several epigenetic modifications in humans that are more likely to happen at certain ontogenetic phases - it seems complete hubris to argue that humans would be somehow exempt from this common mammalian mechanism for individual adaptation. I know there is some evidence to support parental stress responses and risk of mental health disorders later in life; surely epigenetic modifications mediate this relationship to some extent. Now, it's complicated with us because the prefrontal cortex allows for complex psychological responses that modify behavior and stress responses, and we certainly have developmental windows for our psychological development in which parental/environmental influences may alter our behaviors, psychology, and indeed physiology.
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.
This could very well be consistent with Weaver’s findings. Gruenewald seeks to develop a broader theoretical framework in which processes such as epigenetic modifications are mediators of environmental stressors and individual psychological and physiological changes.
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’m not certain that we know the answer to this question, nor is it particularly helpful to know. It doesn’t really matter, from a public health perspective, whether genes contribute to an individual’s response to a negative environment or whether the environment alone influences developmental trajectories. We cannot (at this time) intervene on genetic factors; we can only intervene on environmental factors. Now, if understanding gene-environment interactions truly influences the structure of these interventions (not likely), a role for GxE research may be appropriate in public health policy development.