Childhood stress linked to ageing
Childhood stress could have biological effects that hasten ageing and lead to impulsive behaviour later in life, research suggests.
Scientists found the first evidence of genetic changes associated with early-life stress and adult risk-taking.
Although the work focused on birds, they believe it has important implications for humans.
The study of starlings found that birds exposed to greater stress in the nest went on to develop shorter telomeres - protective caps on the ends of chromosomes, the "packages" of DNA that contain the genetic code.
As adults, they also had a stronger preference for immediate rather than delayed rewards.
Shorter telomeres are linked to faster ageing, age-related conditions including cancer, artery disease and diabetes, and premature death.
Telomeres shorten every time a cell divides until they reach a point where cell division grinds to a halt. The rate at which they shorten varies between individuals, so that some people age more quickly than others.
Lead researcher Professor Melissa Bateson, from the Institute of Neuroscience at Newcastle University, said: "This is all about survival. Animals that suffer stress in early life are likely to be weaker and less healthy and will therefore prioritise immediate survival over long-term benefits.
"What we have demonstrated here is the biological link between impulsive, short-term decision making and early-life experiences.
"People who have experienced extreme adversity during childhood such as abuse or neglect are more likely to demonstrate impulsive behaviours such as gambling in later life and we believe this study goes some way to explaining why that might be."
The findings are published in the journal Proceedings of the Royal Society B.
Starlings live up to 20 years and are often used to understand complex behaviours.
By placing chicks into broods of different sizes the scientists were able to alter stress levels and the rate of telomere shortening. Birds from larger broods experienced greater stress than those taken from a nest of just one or two chicks.
Testing the birds' behaviour 14 months later, the team gave the starlings two choices - a feeder that supplied a small, immediate reward, or one which gave five rewards after a short delay.
"Birds whose telomeres had shortened more during early life, as well as birds who were currently hungrier, had a greater preference for the more immediate rewards," said Prof Bateson.
"Why would you plan for the future when you don't know if you'll make it through to the next day?
"Our findings show that what happens to a starling in the first two weeks of its life has a lasting effect on its telomeres and this in turn predicts adult decision making.
"This means shorter telomeres are markers of bad experiences, and bad experiences predispose adults to taking more risks.
"If, as we believe, this is the same in humans as in other animals then it demonstrates the huge impact that early intervention can have on peoples' future lives."