Effects of early childhood adversity seen in adolescent bodies: Study

How early childhood adversities leave behind impacts, reflected as bodily changes in adolescence, in turn influencing their physical and mental health throughout life, has been uncovered in a new study published in The Lancet Child & Adolescent Health.

Researchers at Massachusetts General Hospital (MGH), Boston, US, involved in this study, had previously showed that exposure to adversity between ages 3 and 5 significantly affected the epigenome of children at age 7, altering biological processes possibly linked to damaging long-term health outcomes.

"We wanted to determine if the epigenetic profiles associated with adversity that we observed in children at age 7 persisted into adolescence and whether the timing of exposure to adversity influenced epigenetic trajectories across development," said first author Alexandre A. Lussier, research fellow at MGH.

Epigenetics is the study of stable changes or mechanisms in cell function not involving DNA alterations, one such mechanism being that of DNA methylation (DNAm).

Measuring DNAm levels conveys information about how genes are expressed, serving as early warning sign of disease processes and helping identify people susceptible to future disease.

"Epigenetics acts at the intersection between a person's genome, which is set at conception and is stable, and the environment, which is always changing," explained Lussier.

"Epigenetic mechanisms, which are sensitive to environmental factors, function like a dimmer switch on our genes, controlling how much of the gene is expressed and how much is turned off over time," said Lussier.

Analysing DNAm in children at three time points - at birth from cord blood, and at ages 7 and 15 from blood, the researchers investigated the timing of exposure to seven adversity types, including neglect, different types of abuse, poverty, and family dysfunction.

They found the greatest DNAm differences at age 15 in children exposed to adversity between ages 3 and 5 compared with adolescents not experiencing adversity.

"The preschool period may be a sensitive period for the biological embedding of childhood adversity that manifests in adolescence," said senior author Erin C. Dunn, Associate Investigator, Center for Genomic Medicine at MGH.

Exposures to single-parent families were particularly linked to more changes in DNAm in adolescence than other types of childhood adversity, such as maternal depression, financial hardship, or abuse.

They also found that DNAm patterns had changed throughout childhood such that at age 15, there were epigenetic changes not present earlier in development. These findings may explain why there are both immediate and latent manifestations of disease among people with histories of childhood adversity.

"These findings are important because they suggest our epigenome may be dynamic across our lifespan," said Dunn.

"In other words, our bodies adapt, in good ways and bad, in response to our life experiences. If true, then interventions could be mounted to help reverse negative epigenetic changes that occur in response to adversity," said Dunn.

The researchers studied children enrolled in the Avon Longitudinal Study of Parents and Children, a 30-year-long prospective birth cohort from the UK that has followed 13,988 children from before birth through early adulthood, collecting multiple measures of childhood adversity and epigenetic profiles across the lives of participants.