Genetic testing – a new study proposes a new link between genes and social environment

What makes you, you? Nature or nurture? The genes you inherited or your environment? Most of us have had this debate at some point. While it may be good for party conversation, turns out the answer is a lot more complex than one or the other. Genetic testing research has shown that it’s not either but rather the combination of nature and nurture that makes us who we are. But the nature of the interaction between our genes and the environment we grow up has not been well understood yet.

A new study conducted by scientists from the University of Michigan, the University of Pennsylvania and Princeton University attempts to
shed some light on this issue. The study suggests that children who are in significantly ‘disadvantaged social environments’ may have poorer health outcomes because of the effects on a factor known as ‘telomere length’ (TL).

Telomeres are stretches of DNA sequence that are at the ends of each of our chromosomes and protect them from degrading or fusing with other chromosomes. You can think of them as similar to the plastic ‘caps’ that we are used to seeing at the ends of shoe laces. The gradual shortening of TL over time is one of the reasons why we age and short telomere length is associated with many diseases including cancer. Research shows that telomere length is a good indicator of longevity. Environmental and lifestyle factors like stress, smoking and obesity have shown to increase the rate at which the telomere shortens. Furthermore, previous studies have suggested that telomere length is a good indicator of how much stress we have been exposed to in our lives.

The current research involved a group of 40 9-year old African American boys in poor social environments and asked two major questions

  1. Do boys growing up in a tough social environment (poverty, unstable families, harsh parenting etc.) have shorter telomere lengths?
  2. Does increased genetic sensitivity alter the effect of social stressors on telomere length?


If the results of this study are shown to be consistent in much larger population samples, we could potentially use telomere length as an ongoing market to measure stress levels in children.


In the population considered, the study found that indeed harsher social environments were associated with a 19% shorter TL in boys. In addition, the researchers also found that the higher educational level of the boys’ mothers was positively correlated with longer TL. This could potentially be because of the direct economic and social impact of education on the family.


In terms of genetic sensitivity, the group studied the correlation between TL and gene variants in dopamine and serotonin pathway genes (which were previously proposed as moderators of genetic sensitivity to stress). The authors found that TL of boys with increased genetic sensitivity scores as determined by serotonin/dopamine genotypes were affected to a greater extent because of stress as compared to those with less sensitivity.

In commenting on the study, Dr Saleem Mohammed PhD, CEO of XCode said, “Though serotonin and dompamine genotypes are established influencers of psychological traits, they are still not ready to serve as a proxy for telomere length. Another important factor to be taken into account is that a much larger sample size is needed to confirm the effects found in the study. Nevertheless, this is a pioneering effort to link gene variants to social stressors through TL as a biomarker and will definitely inspire a lot more research in this area”