How does the experience of traumatic stress in childhood affect one’s life in subsequent years? Leo Enthoven, a PhD student at the Leiden / Amsterdam Center for Drug Research (LACDR) and Leiden University Medical Center (LUMC) studied this subject in a laboratory animal model. He has achieved some remarkable results with mice, but cannot yet say anything about humans.
‘The immediate indication for conducting this research is the presence of a subgroup of patients with complaints of severe depression,’ Enthoven explains. ’Correlated analyses have shown that the majority of this group of depressed patients have suffered traumatic experiences in their childhoods. This may vary from neglect to war experiences.’
Leo Enthoven said, ’I haven’t been able to pinpoint exactly what happens‘. The depression may be partly explained as having a genetic background. ‘The patients with these complaints are already more sensitive to depression compared to people with similar experiences who have no such complaints. The early traumatic childhood experience probably causes these people to develop depression if they suffer a stressful experience later in life. It is difficult to determine exactly what occurs in their brains to make them react in such a way.
Enthoven continued, ‘In humans, it is not possible to determine the neural and molecular causes, as you cannot conduct such experiments on human beings. We do know, however, that the child-parent interaction is extremely important.’ He therefore conducted his research on mice and rats. During a period of eight hours Enthoven removed the mother from her litter of mice. These eight hours are of crucial importance, as the mother is usually absent for a shorter period of time to look for food, for example. The baby mice reacted with a stress response. Removing the mother again on the following days, however, hardly met with any reaction. ’Apparently, the tiny animals had learnt so fast and at a such a young age that the mother was bound to return.
Scent of the nest
The rest of the experiment was more remarkable. At this stage Enthoven compared three groups of mice with different traumatic ‘childhood’ experiences. He placed five-day-old mice individually in a new cage for thirty minutes, removing them from their mother, their siblings and the scent of their nests. As was expected, this produced no reaction as earlier experiments had shown that mice up to twelve days old do not react with stress to such a change.
The second group consisted of mice which, before being placed in the new cage, had first been separated from the mother for eight hours. As expected, this group certainly reacted to the new cage with a stress response. The third group was also placed in a new cage after having been separated from the mother for eight hours. However, this group had already been separated from the mother on the two previous days. This group had not reacted to the eight hour separation but, to Enthoven’s surprise, they reacted all the more intensely to the following thirty minutes in the new cage.
Enthoven said, ’I haven’t been able to pinpoint what happens exactly, but there is every indication that something has changed in the brain. Apparently they are able to learn and trust that the mother will return and at the same time they become more alert to stressful situations.’ The body reacts to stressful situations by producing corticosteron which affects cognitive capacity and memory function. In experiments conducted with the same mice half a year later following these traumatic experiences in their early ‘childhood’, their cognitive performances appear to have developed differently compared to the mice without such traumatic experiences.
Skating on thin ice
Repeated stress situations affect the corticosteron production in the body and this in turn has an adverse effect on the development of the brain. It is, however, premature to draw far-reaching conclusions based on this research and the data can certainly not be extrapolated to the human condition. ’That would equivalent to skating on this ice. But I do, however, believe that this research has come up with useful results which justify further research.’
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