Scientists from the University of South Carolina School of Medicine studied how early traumatic events affect the relationship between the stress hormone cortisol and psychological symptoms in children. The work was published in the journal Development and Psychopathology.
Cortisol is involved in the body's stress response: its level can rise during a difficult task, for example before a performance. The researchers measured the total amount of cortisol over a task and how much it rose. These measures may reflect different aspects of the stress response.
Anxiety and so-called externalizing problems - aggression, anger, rule-breaking - often occur together in children. Past work has produced conflicting results on the link between cortisol and these symptoms.
A team led by Gretchen Perhamus tested whether a history of early trauma could explain the differences. They drew on the theory of adaptive calibration: the stress system adjusts to the level of threat in a child's environment, so the same response may correlate differently with symptoms.
The study included 189 children aged 8 to 15 from a larger study in Charleston. Children and caregivers were interviewed separately about potentially traumatic events. Based on the child's or caregiver's report, 107 participants were assigned to the group that had experienced at least one such event before age six, and 82 to the group that had never encountered them.
During a laboratory visit, each adolescent gave a three-minute speech to a camera, as if auditioning for a TV show about peers. Researchers collected saliva samples before and after the speech to measure cortisol. Usable data were available for 145 participants. Children reported their symptoms themselves during the visit and again two years later.
In adolescents with early trauma, a higher total cortisol level during the task was associated with more pronounced externalizing symptoms at the same time and with such problems predominating over anxiety. Unexpectedly, a higher total cortisol level was associated with lower anxiety in both groups.
Over two years, in the early-trauma group a smaller rise in cortisol predicted a shift toward externalizing problems, while a larger rise predicted a shift toward anxiety. In adolescents without traumatic experience, a larger rise in cortisol predicted a decrease in anxiety over time.
The results depended on which cortisol measure and which symptom comparison were examined. Total cortisol output was associated with current symptoms, while the increase said more about subsequent changes. The groups did not differ in cortisol response.
The authors note limitations. Trauma data were collected retrospectively, and the researchers did not check whether the children experienced additional traumatic events later. Because of the study design, the scientists could not test whether early trauma changed stress responses that then shaped symptoms. Puberty may also affect the stress system. The work used broad symptom measures and a relatively small sample, so the authors say repeat studies are needed.