Study Shows Quality of Maternal-Infant Interaction Can Have Lifelong Biological Consequences

By Heather Duncan

April 17, 2023

Most of us would agree that early childhood experiences can shape our mental and physical health for the rest of our lives, but we tend to think of these effects in social or psychological terms rather than biological. Lead author and recent anthropology PhD graduate Elizabeth Holdsworth, along with researchers Allison Appleton and Lawrence Schell of the Department of Epidemiology and Biostatistics recently published a paper that adds to the growing body of evidence suggesting that early experiences, particularly childhood parental interactions, can alter the epigenome for years to come.

This study focused on the epigenome, the set of instructions that turns genes ‘on’ or ‘off’ depending on the environmental context. Epigenetic mechanisms have become particularly relevant to research in the field of developmental origins of health and disease because they change during sensitive periods of development in response to the environment. Exposure to stress, infection, malnutrition, etc. can fundamentally alter a person’s epigenome, potentially for the rest of their lives.

In this study, Holdsworth, Appleton, and Schell examined a gene associated with a particular endocrine pathway known as the hypothalamic-pituitary-adrenal axis, which is involved in the human stress response. A specific type of epigenetic alteration, known as DNA-methylation, can change the functionality of the gene, which is theorized to lead to problems with social interaction, emotional regulation, and the ability to cope with stress. As the authors explain, “While some research has already explored the relationship between variation in maternal caregiving and infant DNA methylation, few studies have attempted to quantify these caregiving effects independent of adversity in early life (such as a natural disaster), and even fewer have used observational measures of maternal behavior as opposed to self-reported.”

The results of the study, which used data from the Avon Longitudinal Study of Parents and Children, a prospective cohort study tracking the growth and health of children, indicate “with medium confidence that cooler, more awkward maternal behavior at twelve months of age was associated with increased methylation at age seven years, with the strongest association of increased methylation with the highest quartile of maternal cooler, less positive behavior.” In other words, less positive maternal-infant interactions were correlated with higher levels of methylation seven years after the interactions were first recorded.

Holdsworth notes that caution is warranted when interpreting these results. “The fact that the behaviors observed in the study are largely positive or neutral indicates that even small variations in ‘normal’ caregiving behaviors, not just adverse environments, may have an impact on the epigenome," she says. "However, our results do not suggest that mothers should act differently with their infants, because mothers are only one part of an infant's social-emotional environment, which is shaped by many other caregivers too.” Furthermore, “across all studies of maternal–infant interactions, it is important to emphasize that caregiving behavior is also determined by sociocultural factors, such as stress from lack of resources or support, exposure to racism, environmental unpredictability, maternal depression, and poverty.”

Maternal interaction is only one piece of a much larger puzzle, which encompasses the total lived environment that a child experiences as they grow up: “A key takeaway is that a lot more research is needed to understand the role that epigenetics play in the long term physical and emotional development of children. Although infancy is certainly a developmentally sensitive period, further research is needed to clarify how persistent methylation changes in infancy are, particularly whether they do in fact persist through childhood, as this study was not able to directly test.”

It does seem clear though that one sure way to improve the long-term health outcomes of future generations is to support parents. The study also provides more evidence for the importance of our environment and our experiences in shaping who we are and what health problems we may be vulnerable to in the future.