“Nature vs. nurture” is an argument as old as time, and understanding how “nature” is expressed and how “nurture” carries lasting effects in individuals is important in determining health outcomes later in life, especially when it comes to the bond shared between a mother and her child.
As we know, when a mother breastfeeds her child, she provides the baby with antibodies and nutrients to help ensure a healthy immune system, as well as other positive health benefits. A mother who frequently holds and cuddles her baby can also leave a lasting positive impact on the baby’s long-term health.
Obviously, the mother-newborn relationship is a very critical and influential one. The hormone responsible for this bond is called oxytocin. According to a new study out of Max Planck Institute for Human Cognitive and Brain Sciences, it turns out that a mother maybe be able to epigenetically impact the development of the oxytocin system in her child.
As one of the study’s leaders, Tobias Grossmann from the, noted, “Advances in molecular biology, epigenetics in particular, have recently made it possible to investigate the interaction of nature and nurture, in this case infant care, in fine detail. That is exactly what we’ve done here.” Specifically, Grossmann goes on to say, “…in this study we ask whether the mother’s behavior might also have a decisive influence on the development of the baby’s oxytocin system itself.”
Although it has been known that the development of the oxytocin system has a critical influence on adult reactions to social cues and stress responsiveness, very little has been clarified about exactly how this happens.
In order to further understand this complex system, Grossmann joined forces with Kathleen Krol and Jessica Connelly from the University of Virginia with a goal of characterizing epigenetic changes and map them alongside maternal and infant behaviors. Specifically, the researchers focused on DNA methylation levels in the infants, and how they changed depending on the mother’s involvement in play.
DNA methylation is an epigenetic mechanism that involves the addition of a methyl group to the DNA, often resulting in the silencing of gene expression.
A total of 101 pairs of infants and their mothers were included in the study, with specific behaviors characterized at fixed time points. When the infants were 5 months old, a free-play interaction between the infants and their mothers was observed, and behavioral engagement was measured. When the infants were 18 months old, their temperament was measured based on parent reporting.
In parallel, methylation of the oxytocin receptor gene (OTXR) was characterized in the infants, with lower levels of methylation associated with higher OTXR expression. Increased expression allows the infants to respond to oxytocin, which in turn allows them to experience intimacy in their interpersonal relationships—including feeling closer and more connected to the people around them. The researchers’ hypothesis was that infants whose mothers engaged with them more would have less OXTR methylation, and increased OXTR expression.
Their hypothesis was confirmed—and then some. Not only did the researchers find reduced methylation in the children whose mothers, a year earlier, were more engaged with them, but also they saw that the children were already showing clear distinctions in their development. Those with reduced methylation—and increased OTXR expression—had the better temperaments across the board.
This study is a fantastic starting point, but the work in this characterization has only just begun. For starters, the infants whose mothers engaged with them more during the free play likely did not experience this in isolation; they likely consistently had more maternal engagement in their daily lives. Perhaps this was reflected in modalities beyond just the free play type of setting; and what about the effects of interactions beyond just with their mothers?
There is extensive further study needed in order to understand how the various epigenetic “switches” work. But Grossmann, Krol, Connelly, and their teams have made tremendous progress in better understanding the molecular mechanisms that contribute to our individual development—both biologically as well as psychologically.
The power of nurture is strong. Understanding what is most impactful in maximizing infant health can help parents, caregivers, and medical staff make decisions that reinforce the most positive psychosocial development—despite whatever genetic predispositions or other challenges an individual might face.
Source: Krol K, Moulder R, et al. (2019). Epigenetic dynamics in infancy and the impact of maternal engagement Science Advances, 10 (05)
Reference: Max Planck Inst for Human Cognitive and Brain Sci. Mothers’ behavior influences bonding hormone oxytocin in babies. MPIHCBS Press Releases. 16 Oct 2019. Web.
