A recent study, published in the American Journal of Human Biology, has revealed that epigenetic changes can be triggered during infanthood in response to interaction with one’s mother. The study analysed over 100 mother-child pairs, and the findings reveal that the way a parent interacts with their child during their early years can impact the expression of stress-related genes later in life.
A crucial time
Infancy is arguably the most important time in a person’s life, with these years shaping an individual’s personality and behaviours across their lifetime. A significant amount of development occurs during these years, and interactions with one’s parents and caregivers is critical to social and emotional growth. Alongside this, a child’s hypothalamic-pituitary-adrenal (HPA) axis – a neuroendocrine system that governs stress responses – undergoes major changes during this time, potentially influencing a person’s long-term reaction to stress. In the current study, the researchers hypothesised that epigenetic changes may occur early in life in response to interactions between a baby and their primary caregiver, subsequently impacting the expression of genes related to the HPA axis and future stress responses.
A picture is worth 1000 words
This study analysed data from the Avon Longitudinal Study of Parents and Children (ALSPAC). The data includes tracked interactions between mothers and their infants, complemented by blood samples taken from the children at specific time points. For this study, the researchers carefully chose a small subset of the larger ALSPAC cohort. They opted to analyse only those who had singleton births and children who had been subsequently selected for epigenomic analysis at the age of seven, among other constraints. This resulted in the selection of 114 mother-child pairs for analysis.
Part of ALSPAC was an observation of mothers and their 12-month-old children reading a picture book together. The researchers in the current study used this information to determine the “warmth” of the interaction between mother and child. This required an analysis of factors such as physical closeness, verbal communication and the mother’s reactions. A machine-learning algorithm used the data from the picture book observation to determine the warmth, neutrality, or awkwardness of the interactions between mother and child.
The epigenomic analysis of the children, six years after the picture book scenario, involved a measurement of methylation at various CpG loci in the NR3C1 gene. This gene is known to be involved in triggering stress responses via the HPA axis, ultimately leading to a release of cortisol. Overall, methylation at most of the assessed sites were not strongly associated with mother-child relationships, but increased methylation at two sites correlated significantly with more neutral or awkward behaviours. Although this is a relatively small impact, this increased methylation could impact the expression of the gene and subsequently the entire biological response one may have to stress.
As the study did not include any mothers who displayed negative or cold reactions to their children – rather, the behaviours ranged from warm to neutral – the findings suggest that even minor variation in the parent-child relationship can have significant epigenetic impacts. Lead author Elizabeth Holdsworth stated: “There is evidence of a relationship between the quality of maternal-infant interaction and methylation of this gene though these are small effects in response to a relatively small variation in interaction.”
However, the study does not show the full picture, namely because the ALSPAC dataset primarily contains individuals from stable and financially secure households, meaning there may be less inherent stressors in the child’s environment. Moreover, the data does not account for any traumatic events or experiences that may shape a child’s stress response between the age of 12 months and seven years old. Despite this, the work does highlight the importance of high quality, loving interaction between parent and child at a young age, and lays the groundwork for future research.