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June 21, 2012

Bullying, Violence Take a Toll on Children's Cells

Stress, particularly violence, appears to prematurely age children at a cellular level, leaving them vulnerable to disease.

There is growing evidence that early childhood stress can result in physical and mental health consequences that may not manifest until later in life.

Researchers have been attempting to drill down to determine the biological mechanisms for this apparent connection between early stress and increased vulnerability to disease. A recent study looked at the effect of stress at the cellular level in a group of children who had been exposed to stress to see whether they could find any early biochemical signs of stress.  

Such telomere changes as the children showed are considered to be signs of physiologic wear and tear on cells... The researchers speculate that this “wear and tear” may underlie the increased morbidity and mortality seen in adults who have been stressed in childhood.

Children who had been exposed to stress early in life showed significant changes in a portion of their genes called telomeres, sections of repeating DNA sequences at the end of chromosomes. Telomeres are thought to protect the end of the chromosome from destruction. Such telomere changes as the children showed are considered to be signs of physiologic wear and tear on cells. These changes may be related to the aging process.  The researchers speculate that this “wear and tear” may underlie the increased morbidity and mortality seen in adults who have been stressed in childhood.

The investigators followed 2232 children from ages 5 to 10 years. They interviewed their primary care givers three times during the five-year study period about each child's exposures to three types of violence: maternal domestic violence, frequent bullying/victimization, and physical maltreatment by an adult. They used this information to compose cumulative records of each child’s exposure to violence. Within the study group, 54.2% were not exposed to violence; 29.2% were exposed to one type of violence; and 16.5% were exposed to two or more types of violence 

Of the children studied 17% were exposed to domestic violence, 24% were frequently bullied and 26% were maltreated by an adult. Many of the children were already under investigation by police or social services, or were on the child protection register or in foster care because of abuse.

The researchers measured the length of the children's telomeres at the baselines and again in follow up to determine whether there were any changes at the chromosomal level and how these correlated with the children's cumulative stress indices.

Even when the findings took into account the children's sex, socioeconomic status, body mass index and health, the children who were exposed to multiple forms of violence showed the most rapid telomere erosion.

Based on previous studies which had shown shortened telomeres in adults who had experienced childhood adversity and shortened telomeres in middle school children who were institutionalized, the researchers wanted to see if the children exposed to violence during the study period would show shortening of their telomeres compared to controls. This would suggest that the protective function of telomeres might be diminished.

As predicted, children who experienced two or more types of violence exposure showed significantly accelerated the erosion of their telomeres from baseline to follow up measurement compared with children who had one type of violence exposure or who were not exposed to violence at all. Even when the findings took into account the children's sex, socioeconomic status, body mass index and health, the children who were exposed to multiple forms of stress or violence showed the most rapid telomere erosion.

The mechanism for the observed change in the telomeres is not known but oxidative stress and inflammation are known to influence telomere length.  The researchers wonder whether the effect of stress on telomere length is mediated by one of these two pathways and suggest that future research is needed.

The researchers conclude that telomeres can be eroded earlier in life than predicted by chronologic age and that cumulative stress can produce this premature effect. They postulate that this is one way that negative early life experiences can have lasting effects on long-term health. Along with other studies, these findings underscore that efforts to reduce the violence and stress in children's lives are critical for their physical as well as emotional health in the short and long term. Parents, health care providers, and policy makers must all be aware of the necessity to combat the intrusion of violence into the lives of young children.

The study appears in Molecular Psychiatry.

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