Children who grow up in underprivileged households show signs of premature chromosomal aging, reports New Scientist. Moreover, this form of genetic aging might explain why adults who grow up in poor or otherwise stressful environments are more likely to develop serious health problems, such as cancer, later in life.

This chromosomal effect is apparent in 9-year-olds

It's no secret that human beings become more vulnerable to disease as they age. Scientists think that part of this phenomenon can be explained by protective caps found on the end of our chromosomes, called telomeres, which grow shorter as we age. Telomeres help prevent our genes from sustaining various forms of damage, so their shortening can increase a person's likelihood of developing cancer, and of showing general signs of aging. But older adults aren't the only ones who experience telomere shortening. According to a new study published in Proceedings of the National Academy of Sciences, children who grow up in disadvantaged environments also experience significant levels of telomere shortening — and this effect is apparent by the time they turn nine years old.

To reach that conclusion, scientists selected 40 9-year-old African-American boys from a sample of 4,500 children who participated in a multiyear survey study between 1998 and 2000. Researchers found that boys who grew up in poor households had telomeres that were 19 percent shorter than those who grew up in more privileged environments. They also found that children whose mothers changed partners during their childhood had telomeres that were 40 percent shorter than the children whose family structure remained largely unchanged throughout the first nine years of life.

In contrast, children whose mothers had attended college had telomeres that were 35 percent longer than the children of mothers who did not attend university.  "The social environment really conditions the way that these children are living, and their health," Daniel Notterman, a geneticist at Penn State University and co-author of the study, told New Scientist.

Regardless of upbringing, some boys were more susceptible to DNA damage

These results alone can't be used to predict future overall health, because the researchers also noticed that, regardless of upbringing, some boys were more susceptible to DNA damage than others. Some boys who grew up in more privileged environments, for example, demonstrated high levels of genetic sensitivity, and their telomeres were far shorter than those of their peers. These results might seem intuitive — some people appear to be healthier than others, no matter what — but this study is among the first to show that certain people are more sensitive to stress than others, regardless of the environment in which they were brought up.

Of course, a sample size of 40 isn't enough to draw concrete conclusions about the role of a kid's environment in overall genetic health, so researchers are planning to expand the study to a much larger group of children. Should the results prove reproducible, the scientists' conclusions will lend considerable power to the idea that interventions by social workers and therapists in early childhood can significantly improve a person's well-being later in life. As Notterman told New Scientist, this "could be an argument for some people who want to intervene earlier in the lives of children."