Scientists Use Hair Samples to Study the Biology of Mother–Child Bonding

Psychologists have uncovered a new way to study the biology of parenting by examining oxytocin levels preserved in human hair. The approach suggests that chronic hormone patterns may reflect the emotional quality of the bond between a mother and her young child.

The study, published in European Neuropsychopharmacology, found that mothers and children exhibit closely linked oxytocin profiles. In some cases, a mother’s higher hormone baseline appeared to compensate for naturally lower levels in her child.

Oxytocin’s role in human bonding

Oxytocin is produced in the hypothalamus and released both into the bloodstream and within the brain. It is best known for triggering uterine contractions during childbirth and facilitating milk let-down in breastfeeding mothers.

Over the past few decades, research has expanded oxytocin’s role to include empathy, romantic attachment, and caregiving. Scientists increasingly view it as a key biochemical bridge between social experiences and physiological responses.

For toddlers, the early relationship with a primary caregiver, often referred to as a dyad, is central to emotional and social development. Hormones such as oxytocin are believed to help synchronize this relationship, shaping how children learn to trust others and regulate their emotions.

Why hair became a research tool

Previous studies of oxytocin relied primarily on blood, saliva, or urine samples, which capture only momentary hormone levels. These measures can fluctuate rapidly in response to stress, physical activity, or brief social interactions.

Such rapid fluctuations can obscure a person’s long-term baseline, particularly when laboratory visits and interactions with researchers influence stress levels. These short-term snapshots make it difficult to connect hormone patterns with enduring traits or relationship quality.

Hair provides a more stable record because hormones circulating in the bloodstream become incorporated into the growing hair shaft. Since hair grows approximately one centimeter per month, a three-centimeter sample taken near the scalp reflects roughly three months of cumulative hormone exposure.

Inside the mother–child study

The research was led by psychologists Liat Zelikovich Moyal and Florina Uzefovsky at Ben-Gurion University of the Negev in Israel. Their team had previously validated a laboratory method for extracting and measuring oxytocin from human hair.

They recruited twenty-eight mother–child pairs, with mothers averaging thirty-four years of age and children between three and five years old. This developmental stage is considered especially important for the acquisition of social skills and emotional regulation.

Each pair participated in a twenty-minute free-play session in a laboratory room designed to feel natural and unstructured. The interactions were video-recorded so that researchers could later evaluate the emotional quality of the relationship.

Measuring emotional availability

The team used the Emotional Availability Scales, a standardized observational tool, to assess mother–child interactions. The system measures how sensitive, responsive, and attuned the parent is, as well as how engaged and emotionally balanced the child appears.

A mother with high emotional availability responds appropriately to her child’s cues, maintains warmth, and allows independent exploration. An emotionally available child invites the parent into play without becoming overly dependent or withdrawn.

After the play session, researchers collected small hair samples from the back of each participant’s head. In the laboratory, they cut the three centimeters closest to the scalp and analyzed them using an enzyme-linked immunosorbent assay to quantify oxytocin levels.

What the hormone data showed

The results revealed that children had nearly twice the chronic oxytocin levels of their mothers. This difference likely reflects the intense brain development and social learning taking place during early childhood.

Within each family, however, hormone levels were closely aligned. Mothers with higher hair oxytocin levels tended to have children with higher levels as well, suggesting a shared influence of genetics, environment, or both on the biology of the dyad.

Importantly, higher maternal oxytocin levels were associated with better emotional availability scores. Mothers with elevated chronic levels generally displayed warmer, more responsive, and better-attuned behavior toward their children.

A compensatory biological balance?

The relationship between hormones and behavior became more nuanced when child oxytocin levels were taken into account. The positive effect of higher maternal oxytocin on emotional availability was strongest when the child’s oxytocin level was low or average.

When children naturally produced high levels of oxytocin, the mother’s hormone baseline had less visible influence on observed relationship quality. In these dyads, emotional availability tended to be high regardless of maternal hormone levels.

The authors suggest that this pattern may reflect a mutual regulatory system within the dyad. A mother with a strong biological tendency toward bonding may help compensate for a child with lower social hormone levels, while a highly social child may support close bonding even when maternal levels are more modest.

Limits, open questions and next steps

The study’s small sample size, consisting of only twenty-eight pairs, limits how broadly the findings can be generalized. Subgroup analyses in such small samples are statistically fragile, and some interaction effects did not remain robust under more stringent simulations.

As the first study to examine hair oxytocin levels in both parents and children, the findings should be considered preliminary. Larger and more diverse samples will be required to determine whether hair oxytocin can serve as a reliable biomarker of long-term relationship quality.

Future research may follow families over several years to examine how hormone baselines change as children enter school and encounter new social challenges. Researchers may also investigate how factors such as stress, mental health, and parenting interventions influence hair oxytocin levels over time.

Despite its limitations, the study highlights hair analysis as a promising tool for investigating the biology of caregiving. By focusing on chronic hormone patterns rather than short-lived fluctuations, scientists hope to gain a deeper understanding of how close relationships develop and endure.

Article prepared by Alex Morgan.