London: A long-running population study by University of Wisconsin-Madison scientists has found a linked between high levels of family stress in infancy with differences in everyday brain function and anxiety in teenage girls.
The study highlights evidence for a developmental pathway through which early life stress may drive these changes.
The researchers found that babies who lived in homes with stressed mothers were more likely to grow into preschoolers with higher levels of cortisol, a stress hormone. In addition, these girls with higher cortisol also showed less communication between brain areas associated with emotion regulation 14 years later. Last, both high cortisol and differences in brain activity predicted higher levels of adolescent anxiety at age 18.
The young men in the study did not show any of these patterns.
“We wanted to understand how stress early in life impacts patterns of brain development which might lead to anxiety and depression,” said first author Dr. Cory Burghy of the Waisman Laboratory for Brain Imaging and Behavior.
“Young girls who, as preschoolers, had heightened cortisol levels, go on to show lower brain connectivity in important neural pathways for emotion regulation - and that predicts symptoms of anxiety during adolescence,” Dr. Burghy added.
For the current study, Burghy and Dr. Rasmus Birn, assistant professor of psychiatry in the UW School of Medicine and Public Health, used fcMRI to scan the brains of 57 subjects – 28 female and 29 male – to map the strength of connections between the amygdala, an area of the brain known for its sensitivity to negative emotion and threat, and the prefrontal cortex, often associated with helping to process and regulate negative emotion.
Then, they looked back at earlier results and found that girls with weaker connections had, as infants, lived in homes where their mothers had reported higher general levels of stress – which could include symptoms of depression, parenting frustration, marital conflict, feeling overwhelmed in their role as a parent, and/or financial stress.
As four-year-olds, these girls also showed higher levels of cortisol late in the day, measured in saliva, which is thought to demonstrate the stress the children experienced over the course of that day.
Near the time of the scan, researchers queried the teenagers about their anxiety symptoms, and about the stress in their current lives. They found a connection with childhood stress, rather than current stress levels. This suggested that higher cortisol levels in childhood could have modified the girl``s developing brain, leaving weaker connections between the prefrontal cortex and amygdala – an association that explained about 65 percent of the variance in teenage anxiety levels.
Dr. Richard Davidson, professor of psychology and psychiatry, and director of the lab where Burghy is a post-doctoral researcher, said the study “raises important questions to help guide clinicians in preventive strategies that could benefit all children by teaching them to propagate well-being and resilience.”
The study has been published in Nature Neuroscience.