Some children who experience stress in early life develop adult-like brain networks and show signs of ageing more slowly. These children also appear to take longer to progress through puberty, too.
That is what Jonas Miller at Stanford University in California and his colleagues found when they tracked 214 children over two years. The youngsters, aged from 9 to 13 years at the start of the study, were asked whether they had witnessed or experienced a range of stressful experiences, such as a natural disaster, an accident or violence.
At the same time, each child gave a saliva sample. Cells from the sample allowed Miller鈥檚 team to look at the length of telomeres 鈥� DNA caps at the end of chromosomes that shorten as we age.
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The children also had their brains scanned while they looked at images of adult faces expressing various emotions. Based on this, Miller and his colleagues analysed how the children鈥檚 amygdala interacted with the prefrontal cortex 鈥� the part of the brain known to control our behaviour, among other things.
In children, the amygdala and prefrontal cortex tend to fire together. But adult brains show a different pattern 鈥� when the prefrontal cortex is active, it tends to damp down the activity of the amygdala. This is thought to be important for controlling our emotions.
The children who reported experiencing more early life stress tended to show a more adult pattern of brain connectivity, the team found. And this pattern seemed to be associated with slower biological ageing.
When the team looked at the children again two years later, those with more adult-like brain activity seemed to be progressing through puberty more slowly and their telomere shortening was blunted compared to their peers.
The findings provide a rare example of how some changes associated with childhood stress might have a positive outcome for a person, says Nuria Mackes at King鈥檚 College London, who wasn鈥檛 involved in the research. 鈥淚t seems that not all the changes [associated with stress] are bad 鈥� some are protective,鈥� she says.
The children who took part were healthy young people living in the US and had supportive parents. We might not see the same results in children who survive maltreatment or extreme hardship, says Mackes.
And the results don鈥檛 necessarily mean that the children will be more resilient to mental health disorders when they are older, cautions Graeme Fairchild at the University of Bath in the UK.
Cerebral Cortex
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