Previous studies have linked infant stress, which is measured by testing saliva for the stress hormone cortisol, with emotional difficulties later in life.
However, the new study, titled Developmental pathways to amygdala-prefrontal function and internalizing symptoms in adolescence and published in the journal Nature Neuroscience, is the first to show how the part of the brain responsible for regulating emotion changes in teens.
“This is one of the first demonstrations that early stress seems to have an impact on the the way this regulatory circuitry is set up in late adolescence,” says Richard Davidson, a neuroscientist at the University of Wisconsin-Madison, was quoted as saying on the Nature news website.
The study involved comparing brain scans of 66 teenagers and mental health questionnaires they had completed with saliva cortisol samples taken when the same teens were around four-years-old.
The researchers also checked the results against data collected when the participants were young on their mothers reported levels of postnatal depression symptoms, marital conflict, parenting stress, financial stress and role overload.
“Our model indicates that early life stress increases basal cortisol, which in turn modulates emotion-regulation circuitry in adolescence. The functional status of this circuitry at rest predicts both anxious and depressive symptoms and displays strong gender differences, with the effects being stronger in females,” the authors concluded.
“The fact that only females evinced these longitudinal associations between early life stress during infancy, childhood late afternoon basal cortisol and neural connectivity in adolescence extends previous work suggesting that females may be more sensitive to the effects of early life stress on neuroendocrine function,” the study said.
Professor Louise Newman, Director of Monash University’s Centre for Developmental Psychiatry, said the study “adds a very clear association about the impact of early adversity and trauma and the way that shapes the brain.”
“The other issue that needs to be thought about is what can we do in early childhood to promote resilience and to promote healthy brain development,” said Prof Newman, who was not involved in the study.
Girls were more likely to admit to symptoms of anxiety and depression than boys, she said, adding that early childhood stressors could range from poor parenting to outright abuse.
Controlled crying, a method of sleep training that involves leaving an infant to cry and is sometimes linked to increased cortisol in babies, was not necessarily a form of early childhood stress she said.
“We are certainly not saying that controlled crying per se damages people’s brains,” but may become detrimental if it is allowed to go on too long, used on a child too young, or by a parent who is not coping, she said.