In adults, prolonged exposure to stress leads to high levels of the stress hormone cortisol, which damages our brain cells. This damage manifests itself as loss of dendrites, those branches of our brain cells that are used to connect and communicate with other brain cells. Losing dendrites and hence synapses means neural pathways are weakened or lost. This in turn restricts our ability to think clearly, to take in new information, and to remember.
Prolonged exposure to stress in children can manifest itself in the form of behavioural problems.
These may be internalised as anxiety or depression. Or the behaviour may be externalised, resulting in aggressive behaviour and attentional problems.
A contradictory response to ongoing stress had also been noted in children. Researchers were curious as to why some these children with behavioural problems were found to have excessively high levels of cortisol, whilst others had excessively low levels.
A recent study set out to see what if anything led to this variation in the stress response.
It appears that the answer lies in the duration of the stress that the child has been exposed to. The longer the time the individual child had experienced behavioural problems as a result of stress, the lower their level of cortisol was likely to be.
In the study, salivary samples from 96 adolescents were analysed for cortisol levels. These were then matched to cortisol levels associated with behavioural assessments performed initially in childhood and repeated in adolescence.
The two groups of adolescents were differentiated into those with anxiety/depression and those with behaviour problems of aggression and attention difficulties.
Those who had developed anxiety and depression in adolescence were found to have abnormally high levels of cortisol, which is the same response as is seen in adults. But of those who had developed their anxiety or depression at a younger age were found to have abnormally low levels of cortisol. Their stress reaction had become blunted.
The researchers believe that this is a physiological response by the body trying to protect itself from the excess cortisol.
However the problem here is that by developing a blunted emotional response, these young people no longer react normally to other life stresses.
In short term stress, we have the ”flight or fight’ response to keep ourselves safe. If you can see that there is potential danger, such as being about to get run over by a car, or hit by a mistargeted ball, you need your body to react quickly to get you out of harm’s way. If that response is blunted because your cortisol level isn’t high enough, you may not react quickly enough. In the school situation children with a blunted “affect” can no longer see the need to worry. So for example, they no longer see the need to be more diligent with their work if tests or exams are coming up.
In the group of adolescents with aggressive and attentional difficulties, the researchers found abnormally low levels of cortisol in those who had had the behavioural problems from a younger age as well as in adolescence.
Here, the researchers believe that the initial stress, which ultimately leads to aggressive and attentional problems, has often started at a younger age, often around two years. So their brains have been exposed to high cortisol levels for much longer.
The implications from this suggests that in children with behavioural problems, early intervention is warranted rather than a “wait and see’ approach.
The reason being that the blunted response is as bad for the brain as the excess cortisol levels are.
Paula L. Ruttle, Elizabeth A. Shirtcliff, Lisa A. Serbin, Dahlia Ben-Dat Fisher, Dale M. Stack, Alex E. Schwartzman. Disentangling psychobiological mechanisms underlying internalizing and externalizing behaviors in youth: Longitudinal and concurrent associations with cortisol. Hormones and Behavior, 2011; 59 (1): 123 DOI: 10.1016/j.yhbeh.2010.10.015