Mothers’ behavior influences bonding hormone oxytocin in babies

Summary: Greater maternal involvement upregulates the oxytocin system in their babies.

Source: Max Planck Institute

Oxytocin is an extremely important hormone, involved in social interaction and bonding in mammals, including humans. It helps us relate to others. It strengthens trust, closeness in relationships, and can be triggered by eye contact, empathy, or pleasant touch. It’s well known that a new mother’s oxytocin levels can influence her behavior and as a result, the bond she makes with her baby. A new epigenetic study by Kathleen Krol and Jessica Connelly from the University of Virginia and Tobias Grossmann from the Max Planck Institute for Human Cognitive and Brain Sciences now suggests that mothers’ behavior can also have a substantial impact on their children’s developing oxytocin systems.

Childhood marks a dynamic and malleable phase of postnatal development. Many bodily systems are coming online, maturing, or getting tweaked, often setting our psychological and behavioral trajectories well into adulthood. Nature plays an obvious role, shaping us through our genes. But we are also heavily influenced by our interactions, with other people, and with our environment. “It is well known that oxytocin is actively involved in early social, perceptual, and cognitive processes, and, that it influences complex social behaviors,” says Tobias Grossmann. “However, 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. 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”.

The scientists observed a free play interaction between mothers and their five-month-old children. “We collected saliva samples from both the mother and the infant during the visit and then a year later when the child was 18 months old. We were interested in exploring whether the involvement of the mother, in the original play session, would have an influence on the oxytocin receptor gene of the child, a year later. The oxytocin receptor is essential for the hormone oxytocin to exert its effects and the gene can determine how many are produced,” explains Kathleen Krol, a Hartwell postdoctoral fellow in Connelly’s Lab at the University of Virginia who conducted the study together with Tobias Grossmann at MPI CBS in Leipzig.

This shows a mom and her baby

In the study, the scientists observed a free play interaction between mothers and their five-month-old children. The image is credited to MPI CBS.

“We found that epigenetic changes had occurred in the infant’s DNA and that this change was predicted by the quality of the mother’s involvement in the play session. If mothers were particularly involved in the game with their children, there was a greater reduction in DNA methylation of the oxytocin receptor gene one year later. Decreased DNA methylation in this region has previously been associated with increased expression of the oxytocin receptor gene. Thus, greater maternal involvement seems to have the potential to upregulate the oxytocin system in human offspring,” explains the scientist. “Importantly, we also found that the DNA methylation levels reflected infant temperament, which was reported to us by the parents. The children with higher methylation levels at 18-months and presumably lower levels of oxytocin receptor were also more temperamental and less well balanced.”

The results of this study provide a striking example of how we are not simply bound by our genes but are rather the products of a delicate interplay between our blueprints and experiences. Early social interaction with our caregivers, certainly not excluding fathers, can influence our biological and psychological development through epigenetic changes to the oxytocin system. These and related findings highlight the importance of parenting in promoting cross-generational health.

About this neuroscience research article

Source:
Max Planck Institute
Media Contacts:
Tobias Grossmann – Max Planck Institute
Image Source:
The image is credited to MPI CBS.

Original Research: Open access
“Epigenetic dynamics in infancy and the impact of maternal engagement”. Kathleen M. Krol, Robert G. Moulder, Travis S. Lillard, Tobias Grossmann and Jessica J. Connelly.
Science Advances doi:10.1126/sciadv.aay0680.

Abstract

Epigenetic dynamics in infancy and the impact of maternal engagement

The contribution of nature versus nurture to the development of human behavior has been debated for centuries. Here, we offer a piece to this complex puzzle by identifying the human endogenous oxytocin system—known for its critical role in mammalian sociality—as a system sensitive to its early environment and subject to epigenetic change. Recent animal work suggests that early parental care is associated with changes in DNA methylation of conserved regulatory sites within the oxytocin receptor gene (OXTRm). Through dyadic modeling of behavior and OXTRm status across the first year and a half of life, we translated these findings to 101 human mother-infant dyads. We show that OXTRm is dynamic in infancy and its change is predicted by maternal engagement and reflective of behavioral temperament. We provide evidence for an early window of environmental epigenetic regulation of the oxytocin system, facilitating the emergence of individual differences in human behavior.

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