Girls who are stressed and prone to depression may age prematurely, a new study has found.
The research shows girls with a family history of depression respond to stressful situations by releasing higher levels of the hormone cortisol.
Scientists believe that in large amounts, cortisol can damage the immune system and organs, including the brain.
Girls with a history of depression also have telomeres that are shorter by the equivalent of six years in adults, researchers found.
Girls prone to depression respond to stress by producing more of the hormone cortisol. They have shorter telomeres - the caps on the end of chromosomes - which is a sign of ageing
Telomeres are caps on the ends of chromosomes, which get a little shorter every time a cell divides, or as a result of exposure to stress.
Telomere length is like a biological clock corresponding to age, getting shorter as adults grow up.
Previous studies have shown links between shorter telomeres and premature death, more frequent infections, and chronic diseases in adults.
Professor Ian Gotlib, from Stanford University said the findings came as a surprise.
He said: 'I did not think that these girls would have shorter telomeres than their low-risk counterparts — they're too young.'
For the study, researchers recruited 10 to 14-year-old healthy girls with a family history of depression and compared them to healthy girls without that background.
They measured the girls' response to stress tests, asking them to count backward from 100 by seven, and interviewing them about stressful situations.
Before and after the test, the team measured the girls' cortisol levels and also analysed DNA samples for telomere length.
'No one had examined telomere length in young children who are at risk for developing depression,' before the study, Professor Gotlib said.
Healthy but high-risk 12-year-old girls had significantly shorter telomeres - a sign of premature aging.
Exercise has been shown to delay telomere shortening in adults, so girls at high-risk girls should take exercise and learn other stress reduction techniques, experts advised
Professor Gotlib said: 'It's the equivalent in adults of six years of biological aging.
But he added that 'it's not at all clear that that makes them 18, because no one has done this measurement in children'.
Exercise has been shown to delay telomere shortening in adults, so girls at high-risk girls should learn stress reduction techniques, he advised.
Other studies show that neuro-feedback and attention bias training – which redirects attention toward the positive - appear promising.
Other investigators are studying techniques based on mindfulness training.
Professor Gotlib said he and colleagues are continuing to monitor the girls from the original study and it seems as though those with shorter telomeres are more likely to become depressed.
'It's looking like telomere length is predicting who's going to become depressed and who's not' he said.
The study was published in the journal Molecular Psychiatry.
Read more: http://www.dailymail.co.uk/health/article-2818788/Girls-stressed-prone-depression-age-faster-peers.html#ixzz3I1qnoo6a
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