Solving the Cortisol Paradox

Cortisol seems to behave in contradictory ways in children; some youngsters with behavioral problems have abnormally high levels of cortisol, while others with identical problems have abnormally low levels.

In a study published in the journal Hormones and Behavior, researchers at Concordia University and the Centre for Research in Human Development link cortisol levels not simply to behavior problems, but to the length of time individuals have experienced behavior problems.

"We studied the relationship between cortisol levels in young people with problematic behavior such as aggression or depression, and the length of time since the onset of these behaviors," said Paula Ruttle, lead author and PhD candidate at Concordia's Department of Psychology. "Cortisol levels were abnormally high around the time problem behaviors began, but abnormally low when they had been present for a long time."

To obtain subjects' cortisol levels, researchers analyzed saliva samples taken from 96 young people during early adolescence. They then matched cortisol levels to behavioral assessments taken in childhood and again during adolescence. Problem behaviors were classified as either internalizing (depression and anxiety) or externalizing (aggression and attention issues).

Youngsters who developed depression-like symptoms or anxiety problems in adolescence had high levels of cortisol, while those who developed symptoms earlier had abnormally low cortisol levels. Therefore, researchers believe that cortisol levels increase when individuals are first stressed by depression or anxiety, but then decline again if they experience stress for an extended period.

"It seems the body adapts to long-term stress, such as depression, by blunting its normal response," said Lisa Serbin, one of the study’s coauthors. "To take an extreme example, if someone sees a bear in the yard, that person experiences a 'flight or fight' reaction. Stress levels and therefore cortisol levels go up. However, if the same person sees bears in the yard every day for a year, the stress response is blunted. Eventually, cortisol levels become abnormally low."

At first glance, study results from children with aggressive behavior and attention problems seem to contradict this theory. In this group, they found that low levels of cortisol were related to aggressive behavior both during childhood and adolescence. However, the authors contend that since aggressive behavior often begins in the second year of life or earlier, subjects may have been stressed for years before entering the study, resulting in abnormally low cortisol levels.

"This blunted response makes sense from a physiological point of view," said Ruttle. "In the short term, high levels of cortisol help the body respond to stress. However, in the long term, excessive levels of cortisol are linked to a range of physical and mental health problems. So, to protect itself, the body shuts down the cortisol system—but research shows that's not good either."

Individuals with a blunted response to stress may not respond to things that would—and should—make other people nervous. For example, children with long-term behavior problems perform poorly in school. Because of their blunted stress response, these youngsters may not be worried about exams, so they don't bother to prepare as much as their peers.

The study has many significant implications, according to Serbin. "This research suggests interventions should begin as soon as a behavioral problem appears," she said. "For children with severe externalizing problems, this may be very early, perhaps even when they are preschoolers or toddlers.

"We now have evidence that behavioral problems in children are linked to mental and physical health. Taking a 'wait-and-see' attitude may not be the right approach."

Source: Concordia University