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Childhood maltreatment is associated with accelerated biological aging and a tendency to avoid looking at people’s eyes. New research published in PLOS One indicates that these physical and behavioral changes occur independently in children who have suffered abuse. Both of these responses map onto higher rates of emotional and behavioral difficulties, offering researchers a better idea of how early trauma shapes human development.
Biological aging can happen at a different pace than chronological aging. One way scientists measure biological age is by looking at epigenetics. Epigenetics involves chemical modifications to DNA that alter how genes are expressed without changing the underlying genetic code. Specifically, researchers look at DNA methylation, a process where tiny molecular tags attach to certain parts of the genome. As people age, the pattern of these tags changes in a predictable way.
In recent years, researchers have developed epigenetic clocks that use these methylation patterns to estimate a person’s biological age. Extreme stress and trauma have been linked to accelerated epigenetic aging in adults. Being exposed to adverse childhood experiences can force a body to mature faster to cope with unstable environments.
Measuring this accelerated aging in very young children has presented challenges. Older epigenetic clocks were designed for adult tissues and were often unreliable when used on pediatric populations. To fix this, researchers developed the pediatric buccal epigenetic clock. This tool was designed to accurately estimate aging in children using cells collected securely and painlessly from the inside of the cheek.
Along with physical changes, childhood trauma can alter how people interact with their environment. Individuals who experience trauma or social anxiety often display different visual habits. Avoiding eye contact is a common response to severe stress. By looking away, a person might try to disengage from threatening social interactions. Over time, avoiding eye contact can disrupt the development of social skills, as gazing into another person’s eyes is an important part of building emotional bonds.
Keiko Ochiai led a team of scientists to examine these physical and behavioral factors together. Ochiai is a researcher working with the United Graduate School of Child Development at Osaka University in Japan. The research team wanted to see if changes in the epigenetic clock and differences in eye contact happen alongside each other or cause one another. They specifically wanted to study children whose traumatic experiences were officially documented, rather than relying solely on adult memories of childhood trauma.
The researchers recruited 36 children who had experienced physical abuse, emotional abuse, or neglect. These children had been legally removed from the care of their biological parents by child protective services. They were living in residential childcare facilities at the time of the study and had an average age of about six years. The researchers also recruited 60 typically developing children with an average age of about four to five years from the local community to serve as a comparison group.
To evaluate the children’s well-being, the researchers relied on standard psychological evaluations. Caregivers and parents filled out the Strengths and Difficulties Questionnaire. This survey asks caregivers to rate a child on a variety of attributes, including emotional symptoms, peer relationship issues, and prosocial behaviors. By tallying these reports, the researchers gained a broader picture of how well each child was adapting to their social environment.
To measure biological aging, the team collected cheek swabs from all the children. They extracted DNA from the cells lining the inside of the cheeks. The team then analyzed thousands of molecular locations on the DNA to read the methylation tags. They used the pediatric clock formula to calculate each child’s biological age. The researchers then compared this biological age to the child’s actual chronological age to calculate whether their aging was accelerated.
The researchers also evaluated how the children processed social information. They seated each child in front of an eye-tracking monitor in a quiet room. The children underwent a brief calibration process where they tracked an animated animal on the screen. Then, the screen played short videos featuring different social cues. These videos included people and geometric patterns, the biological motion of a human body, objects with pointing gestures, and human faces.
As the children watched the videos, the equipment recorded exactly where they were looking. The team divided the screen into specific areas of interest. They designated highly social areas, such as the eyes on a human face or the upright figure of a person. They also noted less social areas, like the mouth on a face or background areas in the video. The system measured how much of the child’s gaze was fixated on these specific areas.
When analyzing the genetic data, the researchers found that the maltreated children exhibited accelerated biological aging compared to the typically developing children. The epigenetic clocks of the maltreated children ticked faster than their actual ages. The researchers noted that while the overall difference was moderate in size, even subtle changes in biological aging during early childhood could have cumulative impacts later in life, such as earlier onset of puberty.
The eye-tracking data revealed specific differences in how the children looked at human faces. The maltreated children spent less time fixating on the eye region of the faces on the screen. Instead, their gaze varied more across other areas like the mouth or the background. The two groups did not show differences in how they looked at other types of social cues, like moving bodies or pointing fingers. The behavioral change was highly specific to human faces.
The team explored whether specific details of the children’s trauma history affected these outcomes. They looked at the type of maltreatment, the duration of the abuse, and the time that had passed since the children were removed from their homes. None of these specific historical factors changed the degree of biological aging or the amount of time spent looking at eyes. However, children who had experienced multiple types of maltreatment scored higher on the behavioral difficulty questionnaire.
The researchers then looked for mathematical relationships among the epigenetic data, the eye-tracking data, and the behavioral questionnaires. They found that spending less time looking at eyes was associated with faster biological aging. Both of these individual traits were also linked to higher scores on the behavioral difficulty questionnaire. This suggested a relationship among the biological clock, visual habits, and emotional health.
The team used a statistical technique to see if these factors functioned like falling dominoes, where one caused the next. They mapped out a model to test if accelerated aging caused the children to avoid eye contact, which in turn caused the behavioral problems. The statistical model did not support this chain reaction. Instead, it indicated that accelerated aging and reduced eye contact operate in parallel. Both traits were independently associated with the behavioral problems seen in the maltreated children.
To explain these parallel effects, the researchers note that epigenetic changes can alter the way specific genes influence social behaviors. Altered gene expression could disrupt social development from an inner biological level. At the same time, children who do not look at eyes miss out on important visual cues. Previous research has linked reduced eye contact to lower levels of oxytocin, a hormone involved in building trust and forming emotional bonds. This lack of attachment experience likely fuels higher rates of social and emotional difficulties.
The authors note a few limitations to their research. The study design was cross-sectional, examining a single point in time rather than tracking the children over many years. Because of this snapshot effect, the researchers cannot state that child maltreatment directly causes the observed changes in aging and eye gaze. Causality can only be proven through different types of experimental methodologies that track changes as they occur.
The size of the study sample was relatively small, though it was sufficient for the statistical tests used. There was also an age difference between the maltreated children and the comparison group. The researchers adjusted their statistical models to account for this age gap, but comparing groups of the exact same age would provide stronger evidence. The researchers also noted that they lacked data on adult populations, making it hard to know if these exact structural changes persist into adulthood.
Future investigations will likely track children over longer periods to see how biological aging and social behaviors develop over time. This approach could help scientists determine if moving children to stable, supportive environments can slow the accelerated epigenetic aging process. It might also show whether early interventions can improve social interactions and restore normal eye contact behaviors.
Eventually, identifying these biological and behavioral markers could assist medical professionals in evaluating the health and social needs of young trauma survivors. These structural and behavioral adaptations appear to be tied closely to the instability of the children’s early environments. By reading these biological and behavioral markers, psychologists might one day tailor treatments to address both the physical toll of trauma and its everyday social consequences.
The study, “Behavioral and emotional difficulties in maltreated children: Associations with epigenetic clock changes and visual attention to social cues,” was authored by Keiko Ochiai, Shota Nishitani, Akiko Yao, Daiki Hiraoka, Natasha Y.S. Kawata, Shizuka Suzuki, Takashi X. Fujisawa, and Akemi Tomoda.
