Genetics or Geography? Children’s Physical and Mental Health

Updated: Jan 24


Does nature or nurture have a greater effect on children's health? There is compelling evidence revealing that the relationship between geography and the quality of physical and mental health surpasses the associations between genetic precursors to health. One study from the Columbia Mailman School of Public Health and the University of California at Irvine discovered that the genetic factors that contribute to obesity among adolescents were inadequate to explain the disproportionate rates of obesity among children from low-income communities versus those from more affluent ones. This discovery mirrored their findings for mental health problems as well; children from impoverished communities had higher rates of mental health disorders, despite little evidence suggesting that genetic factors were the root cause of this difference [2, 5]. Similarly, a longitudinal study conducted on data from 1995-2018 found that children who lived in and out of poor neighborhoods had significantly higher diastolic blood pressure when compared to children who had always lived in wealthy neighborhoods. In addition, children who had recently left poor neighborhoods still had 46% higher odds of developing obesity and 52% higher odds of developing hypertension as adults [7].


To further analyze the effects of the environment on children’s development, researchers have also looked into the way living in a lower socioeconomic status (SES) household affects brain development in children [10]. Many studies have found that children from low-income neighborhoods and, more specifically, low SES households, scored significantly lower on a variety of cognitive function tests. When individual SES is controlled for, children from violent neighborhoods also scored lower on these cognitive tests.


To explain this difference, scientists formulated a hypothesis stating that chronic stress leads to the overproduction of glucocorticoids, resulting in desensitized glucocorticoid receptors in the hippocampus. This desensitization could potentially lead to altered development of the hippocampus, an area of the brain largely responsible for learning and memory. Thus, chronic stress, prevalent in lower-income neighborhoods, directly affects cognitive development, especially in children [10]. Oftentimes, this stress is caused by neighborhood violence and can lead to harmful and long lasting consequences, irrespective of genetics. In a study in New Orleans, researchers found that cortisol levels in children from neighborhoods with more liquor and convenience stores were significantly more likely to stay elevated after reactivity and stress tests. Similar results were found for children exposed to domestic violence and violent crime [11]. These are concerning findings as high cortisol levels have repeatedly been found to be associated with hypertension, dyslipidemia, obesity, and many other health conditions [12]. This study also found that an increased density of liquor and convenience stores was inversely associated with telomere length, yet another factor that has been found to be directly related to poor health [11]. Neighborhood violence manifests itself in a variety of manners, with a widespread effect on many facets of biological and cellular markers in children, which in turn reveal themselves in physical and mental health.


The use of policy and environmental intervention is often a direct way to tackle these issues by encouraging policymakers and advocating for the creation of healthier communities. For example, one study analyzed the difference over a four year period of introducing urban pedestrian trails in an attempt to encourage increased physical activity. The introduction of these community assets indeed increased the physical activity levels among the children, with children two times more likely to engage in physical activity with the implementation of these features [6]. Another study similarly found that an increased percentage of green space was moderately and negatively associated with neighborhood problems, defined by disorder and crime, but positively associated with healthy weight status and prosocial behaviors [9]. Physical and mental health are undeniably linked, therefore the introduction of green spaces into communities can improve both the physical and mental health of children which, in turn, can better their cognitive development.


However, improving neighborhoods through physical changes such as adding green spaces is not enough to improve childrens’ health because low-income neighborhood improvements can negatively affect housing affordability. If housing prices increase after neighborhoods are improved, low-income families are often displaced out of the neighborhoods and higher-income families move in [4]. Hence, policies meant to improve the lives of those with lower SES, ultimately, do not benefit this targeted group. As a result, it is crucial that policymakers prioritize making broad changes such as policies to reduce crime in neighborhoods, as this has been shown to avert this gentrification [4]. There are a variety of policies that can be explored and implemented to achieve this. For example, since research has shown that alcohol plays a role in about forty percent of violent crimes, policies such as increasing the alcohol tax or creating stricter licensing for alcohol outlets may lead to a decrease in violent crime [8]. A different, more holistic approach can be to invest in community substance abuse prevention initiatives which has also been shown to reduce crime [4].


The further implementation of policies that transform neighborhoods in these positive ways is a crucial step in addressing the root causes of the concerning trends in children’s health. Many of these concerning trends are not rooted in genetics, but rather come down to neighborhood and community makeup. Children are the future, so ensuring a healthy present for them ensures a healthy future for us all. By examining policies that may mitigate the aforementioned health trends, it will take us one step closer to just that.


References:

  1. Acevedo-Garcia, D., McArdle, N., Noelke, C., Huber, R., Huntington, N., & Sofer, N. (2020, January 17). A snapshot of child opportunity across the U.S. Diversity Data Kids. Retrieved November 4, 2021, from https://www.diversitydatakids.org/research-library/data-visualization/snapshot-child-opportunity-across-us

  2. Belsky, D. W., Caspi, A., Arseneault, L., Corcoran, D. L., Domingue, B. W., Harris, K. M., Houts, R. M., Mill, J. S., Moffitt, T. E., Prinz, J., Sugden, K., Wertz, J., Williams, B., & Odgers, C. L. (2019). Genetics and the geography of health, behaviour and attainment. Nature Human Behaviour, 3(6), 576–586. https://doi.org/10.1038/s41562-019-0562-1

  3. Ellen, I. G., & Glied, S. (2015). Housing, Neighborhoods, and Children’s Health. Education Resources Information Center. Retrieved November 3, 2021, from https://files.eric.ed.gov/fulltext/EJ1062946.pdf.

  4. Frakt, A. (2017, April 24). Spend a dollar on drug treatment, and save more on crime reduction. The New York Times. Retrieved December 1, 2021, from https://www.nytimes.com/2017/04/24/upshot/spend-a-dollar-on-drug-treatment-and-save-more-on-crime-reduction.html.

  5. Genetic code and postal code: Both matter for Children's Health. Search the website. (2019, April 8). Retrieved November 13, 2021, from https://www.publichealth.columbia.edu/public-health-now/news/genetic-code-and-postal-code-both-matter-children%E2%80%99s-health.

  6. Heath, G. W., & Bilderback, J. (2019). Grow healthy together: Effects of policy and environmental interventions on physical activity among urban children and Youth. Journal of Physical Activity and Health, 16(2), 172–176. https://doi.org/10.1123/jpah.2018-0026

  7. Lippert, A. M., Evans, C. R., Razak, F., & Subramanian, S. V. (2017). Associations of continuity and change in early neighborhood poverty with adult cardiometabolic biomarkers in the United States: Results from the National Longitudinal Study of adolescent to Adult Health, 1995–2008. American Journal of Epidemiology, 185(9), 765–776. https://doi.org/10.1093/aje/kww206

  8. Lopez, G. (2016, February 15). 6 proven policies for reducing crime and violence without gun control. Vox. Retrieved December 1, 2021, from https://www.vox.com/2016/2/15/10981274/crime-violence-policies-guns.

  9. Odgers, C. L., Caspi, A., Bates, C. J., Sampson, R. J., & Moffitt, T. E. (2012). Systematic social observation of children’s neighborhoods using google street view: A reliable and cost-effective method. Journal of Child Psychology and Psychiatry, 53(10), 1009–1017. https://doi.org/10.1111/j.1469-7610.2012.02565.x

  10. Taylor, R. L., Cooper, S. R., Jackson, J. J., & Barch, D. M. (2020). Assessment of neighborhood poverty, cognitive function, and prefrontal and hippocampal volumes in children. JAMA Network Open, 3(11). https://doi.org/10.1001/jamanetworkopen.2020.23774

  11. Theall, K. P., Shirtcliff, E. A., Dismukes, A. R., Wallace, M., & Drury, S. S. (2017). Association Between Neighborhood Violence and Biological Stress in Children. JAMA pediatrics, 171(1), 53–60. https://doi.org/10.1001/jamapediatrics.2016.2321

  12. Whitworth, J. A., Williamson, P. M., Mangos, G., & Kelly, J. J. (2005). Cardiovascular consequences of cortisol excess. Vascular health and risk management, 1(4), 291–299. https://doi.org/10.2147/vhrm.2005.1.4.291

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