According to a new study children who are victims of bullying and violence have DNA wear-and-tear that is normally associated with aging. This means they age faster than other kids.
The study finds that violence-related stress in children affects telomeres - special DNA sequences found at the tips of chromosomes. Telomeres, which prevent DNA from unravelling, get shorter each time cells divide, which limits the number of times cells can divide. Shorter telomeres have been linked to poorer survival and chronic diseases. Previous research has shown that smoking, obesity, mental-health disorders and stress may accelerate the process of telomere loss. This suggests that telomere length may reflect a person's biological age as well as their chronological age.
For this latest study the Duke University researchers analyzed data from a British study that tracked 1,100 families with twins from the twins' birth in the 1990s. DNA samples were collected from the children when they were 5 and 10 years old.
The researchers tracked 2,232 children born between 1994 and 1995 in England and Wales. The researchers focused on 236 children whom they followed from age 5 to 10. Nearly half of the children had had some exposure to violence, either in the form of observing violent acts against their mother, being bullied themselves, or being the victim of aggressive acts by an adult.
By the 10-year-old time point, 17 percent of the children had experienced domestic violence in their households, 24.2 percent had been frequently bullied and 26.7 percent had been physically abused by an adult, according to interviews with the children's mothers. (Some kids were already in protective custody as a result of this abuse.) Because some children experienced more than one type of violence, the researchers split them into groups: kids who hadn't experienced violence (54.2 percent), kids who had experienced one type of violence (29.2 percent), and kids who had experienced two or more types of violence (16.5 percent).
The team noted that children with a history of two or more kinds of violent exposures -- such as domestic violence, frequent bullying or physical abuse by an adult -- had significantly more telomere loss than other children. The study was published April 25 in the journal Molecular Psychiatry.
“This is the first time it has been shown that our telomeres can shorten at a faster rate even at a really young age, while kids are still experiencing stress,” Idan Shalev, a postdoctoral researcher in psychology and neuroscience at Duke University's Institute for Genome Sciences & Policy, said in a university news release.
The findings suggest that protecting children from harm may benefit their long-term health. “An ounce of prevention is worth a pound of cure,” study co-leader Terrie Moffitt, a professor of psychology and neuroscience, said in the news release. “Some of the billions of dollars spent on diseases of aging such as diabetes, heart disease and dementia might be better invested in protecting children from harm.”
The study is the first to follow children and track changes to their DNA that might be related to their exposure to violence. Even after adjusting for other socioeconomic and physical factors that affect premature cell aging, such as poverty or obesity, the relationship remained.
The study also adjusted for another important factor that previous studies were not able to account for — the natural variation in telomere lengths in individual people. By comparing the children’s telomere lengths at two different time periods, Shalev and his colleagues were able to avoid possible bias due to the fact that, for example, telomeres actually lengthen as they age in a small percentage of people. The comparison also allowed them to account for the fact that children exposed to violence tend to be less healthy as adolescents and adults, which could affect cell aging as well.
Youth violence is widespread in the U.S. today. The CDC states that it's the second leading cause of death among people between the ages of 10 and 24, and that nationwide, about 20% of students in grades 9-12 were bullied in 2009.
Victor Fornari, director of child and adolescent psychiatry at the Zucker Hillside Hospital in Glen Oaks, N.Y., said the new findings make perfect sense. “This article really points to a potential biological [indicator] that helps explain some of the differences in the brains of children who have experienced significant trauma and stress,” he said. “It is exciting to have this kind of window into what may be causing significant health problems that traumatized young people have as they grow up,” Fornari said. “Chronic maltreatment may have deleterious effects on children's health, brain, and the way in which their brain functions. There is no good evidence to stay that this is reversible.”
“It's possible, and likely, that faster telomere shortening in childhood could put us on a more rapid trajectory of aging and early onset of disease as adults,” said Elissa Epel, in an email to WebMD. She is the AME Laboratory director at the University of California, San Francisco. “The residue of childhood trauma may even manifest decades later, in adults. Now we have some evidence that indeed children's immune system aging can be adversely affected by severe stress early in childhood, a scar that could possibly last decades later. This study underscores the vital importance of reducing violent exposures for children -- both serious bullying and abuse in the family.”
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