Stressful social environments can leave lasting marks on a young individual’s chromosomes. Repetitive DNA sequences, called telomeres, protect the ends of each chromosome from deterioration or from fusion with neighboring chromosomes. Longer telomeres have been linked to longer lives in some studies.
A new study, published in the Proceedings of the National Academy of Sciences, suggests that children from poor and unstable homes have shorter telomeres compared to those from nurturing and stable families with improved socioeconomic status.
The researchers collected DNA samples and socioeconomic data from participants in the Fragile Families and Child Wellbeing Study, an effort funded by the U.S. National Institutes of Health to track nearly 5,000 children. The majority of participants were born to unmarried parents in large U.S. cities in 1998–2000.
The children's social environments were rated based on their mother's level of education, the ratio of a family’s income to needs, harsh parenting, and whether family structure was stable.
The DNA of 40 boys selected for the study were from major US cities at age nine. The researchers found that the telomeres of children from harsh home environments were 19 percent shorter than those of children from advantaged backgrounds. The telomeres of boys whose mothers had a high school diploma were 32 percent longer compared with boys whose mothers had not finished high school. Also, the children who came from steady families had 40 percent longer telomeres than those of children who had experienced many changes in family structure, such as a parent with multiple partners.
The length of telomeres is often viewed as a biomarker of chronic stress. The study found that the link between stressful home environments and telomere length is moderated by genetic variations in pathways that process two neurotransmitters in the brain, serotonin and dopamine. Some of the genes studied in previous studies are TPH2and 5-HTT. Some variations of these genes are perceived to increase the sensitivity of external risks.
Children with more than two “sensitizing” variants of these genes were strongly influenced by their home environments. The boys had the shortest telomeres in stressful homes, and the longest telomeres in advantaged environments.
The researchers hope to expand its analysis of approximately 2,500 children and their mothers to see if these preliminary findings hold. Lead author, Daniel Notterman, a molecular biologist at Pennsylvania State University in Hershey, believes early intervention practices may help to moderate the effects of adversity on children’s health since the effects of stress are tangible by the age of nine.