The stress of growing up in a poor and unstable household affects 9-year-old children at the genetic level, shortening the part of their chromosomes that scientists say is a key factor in aging and disease. The researchers say their findings are the first to document this type of genetic change among children coming from poor (mostly minority families) and provide strong evidence of the importance of early childhood intervention in vulnerable communities.
Research done in 2014 showed that growing up in a poor and unstable environment affects 9-year-old children at the genetic level. The researchers examined the DNA of a small group of 9-year-old African-American boys who experienced chronic stress as a result of growing up in families with poor socioeconomic status. The results showed that the body sequences of boys were shorter than boys of the same age and ethnicity who came from families of more stable and families of better socio-economic backgrounds.
These body sequences are repetitive DNA sequences located at the ends of chromosomes that function as a kind of cap to protect genetic information when DNA is replicated. They become shorter each time DNA is replicated, and studies have shown that stress accelerates that shortening, serving as a type of genetic depletion that is similar to aging.
The researchers were surprised to find significant links between shortening the physical performance of low-income boys, low maternal education, family instability, and harsh parenting style, compared to boys coming from higher-income higher-income families and more stable and nurturing backgrounds.
In addition, disadvantaged boys who had a genetic sensitivity to dopamine and serotonin – neurotransmitters associated with happiness and feelings of satisfaction – experienced a rapid shortening of body indicators, pushing them further on the path to stress and disease.
“Initially, we thought such results would show in the mothers of these children,” said Colter Mitchell, lead author of the study and a faculty researcher at the Center for Population Studies and the University of Michigan Research Center. “But I think it’s more surprising that we got results like this in a 9-year-old boy.”
Physical poverty tribute
Scientists have previously documented how the stress of poverty can have an intense physical effect on people, literally leading them to some kind of disease. But the relationship between poverty and physical indicators is a relatively new field of research. Elizabeth Blackburn, a professor of biology and physiology at the University of California, San Francisco, pioneered modern research on bodily indicators by deciphering their molecular structure and won the 2009 Nobel Prize for her work.
Subsequent studies have shown that truncated body sequences can serve as a genetic indicator for signs of aging and disease in adults. A recent study examined the link between stressful environment and length of body sequences in children, finding that exposure to violence, for example, means shorter body sequences in 10-year-olds and that babies and young children who spent more time in Romanian orphanages have shorter body sequences than those who stayed in them longer.
But most of this research has been conducted on white children, Mitchell said. He and his team wanted to know if the length of body sequences could serve as a biomarker for the stressful effects of poverty and family instability before disadvantaged children experience these effects as adults in the form of illness.
To find out, the researchers looked at a group of nearly 3,000 black nine-year-old boys and their mothers who were part of a study on families at risk at Princeton and Columbia universities. This project follows a large population of children born between 1998 and 2000 in urban areas of the United States, mostly from cohabitation.
They selected a small sample of 40 boys: 20 of those who were most at risk in terms of family income, mother’s level of education, whether the mother had ever suffered from depression, rude parenting style, and stability of the family structure. – factors that are considered to have a major impact on stress in the child’s environment – and 20 of those that were most favorable in terms of these factors.
During their analysis, they found a significant association between disadvantaged boys and shortened body sequence lengths, compared to their peers from favorable socioeconomic backgrounds. One example is that the doubling of family income shows an association with body sequences, which in this case were 5% longer. Children whose mothers completed high school had body sequences that were 32% longer; and in the case of mothers attending some college, these body sequences were 35% longer.
Further, the researchers took saliva samples from the boys to test for the presence of genetic markers for dopamine and serotonin sensitivity.
and found that this genetic tendency exacerbates the effect of shortening body sequences in disadvantaged children.
To illustrate what this genetic tendency means, Mitchell turned to the usual analogy made by scientists. “Some people are dandelions; regardless of the environment, they turn out the same and are resilient when faced with stressful circumstances. Other people are orchids; they are greatly influenced by their environment. Under good circumstances, they bloom”, but, as Mitchell explains, “If something seems to go wrong, they just fall apart.”
“People who are presented as orchids,” Mitchell continues, “are the ones who have a genetic marker for dopamine and serotonin sensitivity.” “It amplifies any signal they receive from the environment.” “If it’s a good environment, then it’s great, but if you’re constantly in an unfavorable environment, then you have the worst result.”
In terms of evolution and survival of the fittest, owning that biomarker is not such a good thing when a person lives in a stressful environment. “In general, you want people to be insensitive to all kinds of environments,” Mitchell explains, “so they can adapt and survive in all circumstances.”
However, he also points out that genetic susceptibility – as well as his team’s findings – suggest that early intervention in the lives of poor children can have a profound effect.
“Children from socio-economically disadvantaged families, too, can benefit most from any intervention,” he said, adding that the results are “constant support for the idea that we need to have early childhood interventions that help mitigate the effects of this kind of negative environment. And some of those kids will benefit a lot more than we can imagine. ”
The results of the research were published in the Proceedings of the National Academy of Sciences.