School children in class.
(photo credit: MARC ISRAEL SELLEM)
Children affected by stress – such as terror attacks – should not be treated by psychologists and psychiatrists in the same way as adults, according to University of Haifa neurobiologist Prof. Mouna Maroun.
She reached this conclusion, just published in Biological Psychiatry, based on the similarity between the coping mechanisms for stress that are shared by rodents and humans.
Her rat studies showed that youngsters’ brains cope with stress differently.
Conventional wisdom has led therapists to think that both age groups can be treated the same way.
But, said Maroun, working with research student Rachel Schayek, young rats extinguished fear much more rapidly. Moreover, while in adult rats the plasticity of the prefrontal cortex declined under stress, among young rats a different mechanism actually enhanced plasticity.
Neuroplasticity refers to changes in neural pathways and gaps between neurons (synapses) resulting from changes in behavior, environment, neural processes, thinking and emotions.
Until now, said the Haifa team, it was thought that it works similarly at all ages. Maroun said she always felt instinctively that this assumption was wrong.
“It all began when I knocked my head while I was in a swimming pool – a mild form of trauma, but enough to persuade me not to go back into a swimming pool for a long time. But children who were in the pool and who knocked themselves much more badly than I did didn’t think twice about jumping straight back into the water. When I saw this, I realized that this was something I needed to examine in the laboratory.”
Childhood is a period when the brain and the prefrontal cortex are still developing, so there is no reason that the mechanism of action in adults and young people should be the same,” stressed Maroun, who heads the university’s neurobiology department.
During exposure to a stress experience, two cerebral mechanisms make it possible to respond efficiently to fear, on the one hand, but also to return to normal once the event ends. During such an event, a mechanism located in the brain’s amygdala effectively tells us that we are in a frightening situation and must act by fighting, escaping or freezing on the spot. After the event, a “fear extinction” process begins in the prefrontal cortex and effectively returns the body to its routine state. When the return to normal fails to function properly, we delay the fear extinction mechanism and continue to experience reactions of fear, leading to symptoms of anxiety and post-trauma.
Since exposure to stress after the learning of fear associations is known to delay fear extinction among adults and has been thought to work the same also among children, the researchers also included this factor in the equation. Young rats that had been weaned and adult rodents were exposed to a mild traumatic event.
Some of them were then placed on an elevated platform, creating exposure to stress, while the control groups were not exposed to stress. The adult animals reacted as expected, showing strong fear responses compared to the rats not exposed to trauma. The group that was not exposed to stress lost their fear more rapidly than the group that was exposed.
But among the young rats, the situation was completely reversed.
The fear reactions of the rats exposed to trauma were much lower and the fear extinction time was much shorter than among the adult rats. In addition, the young rats exposed to stress actually lost their fear faster than their peers not exposed to stress. Thus, exposure to stress among the young rats actually sped up the return to routine and significantly reduced fear reactions, the researchers said.
After this behavioral examination, the investigators examined physiological changes to the brain and found a similar pattern. Prefrontal cortex plasticity in the area responsible for fear extinction was extremely high among the young rats exposed to stress; but in stressed adult rats, the plasticity level was extremely low. A brain receptor called NMDA – when blocked in stressed adult rats – helped eliminate stress but had no impact on young rats, so the mechanism is not identical in all age groups.
Hence, the investigators reached the conclusion that medications and other treatments used to treat child trauma victims should not be the same given to traumatized adults.
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