1. 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? Please consider this both in general and in respect to your particular area of interest.
It is easy to see how both genes and environment individually play roles in future health and disease, and I agree with Hertzmann and Boyce that the interaction between genes and environment can serve as a potent mediator of outcomes. I was once told that “genes load the gun, environment pulls the trigger.” This is a colorful (if not overly facile) way of stating a similar point. However, Hertzmann and Boyce take this argument a step further and suggest that not only is every outcome the result of a GxE interaction, but that genes and environment may synergize such that environmental factors shape genes which in turn lend themselves to social and health disparities in the environment. The most direct evidence they provide for this sociobiological interaction comes from animal studies, which should be applied to humans and human society with caution. On its face, the idea that there are both genetic and environmental determinants of health is valid to me; this interaction certainly fuels health disparities across social and economic lines. Quantifying the effect of these interactions is difficult or impossible though, because, judging from the evidence provided in the article, we are far from a coherent understanding of how much genes and environmental factors affect outcomes and affect each other.
2. Discuss implications of epigenetic mechanisms of disease for intergenerational effects on health disparities, as well as for interventions designed to address health disparities.
If epigenetic changes are heritable, there are huge potential implications for the intergenerational promulgation of health disparities. The papers by Barcelona de Mendoza et al. and Robinette et al. present evidence that social & environmental factors (e.g. the early childhood stresses associated with poverty) can induce epigenetic changes that alter DNA expression and affect future health. As a result, environmental hardship in one generation can translate to health risks in the next generation; those very health risks will in turn augment disparities and make it more likely the sickest members of society will continue to suffer the same environmental risk factors as their forbears. The ramifications of epigenetics on public health is vast and highlights the notion that effective interventions must address the socioeconomic factors that affect environments. For example, improving access to good medical care is only partially effective if patients go home to unstable environments, stifled by structural racism. Effective interventions will get down to the neighborhood level to address those environmental stressors most likely to cause maladaptive epigenetic changes.
3. Discuss how the findings in the Robinette paper relate to socioecological model we are using in this course – e.g. briefly describe how the different levels displayed in this model are related to each other in this paper.
Robinette et al. (2016) laid out the connections between environmental stresses and physiology, using allostatic load as a measure of various health outcomes and neighborhood income. The authors use “low SES neighborhood” as a proxy for accumulated psychological, social, and physical stressors that put inhabitants at risk for poor health outcomes. This approach mirrors the socioecological model in that it weaves through the layers that comprise the lived experience and shape health. Low-resource neighborhoods are disproportionately affected by crime and violence. Fears over personal safety lead to stress and may affect neighborhood social cohesion, sowing the seeds of isolation. Neighborhood crime deters outdoor physical activity, depriving residents of options for exercise and failing to support healthy behaviors. These neighborhoods are also farther from economic opportunity, cementing income disparities. Sources of affordable, healthy food are rare, raising risks of obesity and dyslipidemia. Poor living conditions in low SES neighborhoods may contribute to stress and poor sleep. Each of these “hits” can affect health, though in many different ways. Robinette and co-authors manage this by using allostatic load as a composite measure of the ways that stresses accumulating at each level of the socioecological model can shape health.