Stress takes a toll on both mind and body.
Intuitively, that's not a big surprise. Many studies have found links among stress, depression and disease. But scientists didn't really know which came first: stress, depression or changes in the body.
Stanford psychologist Ian Gotlib and colleagues at Stanford, Northwestern University and the University of California, San Francisco found one way to address this question.
They studied healthy girls at high risk for developing depression because they have a family history of the disorder. These girls were stressed out, and they responded to stress by releasing much higher levels of the hormone cortisol.
The girls also had telomeres that were shorter by the equivalent of six years in adults. Telomeres are caps on the ends of chromosomes. Every time a cell divides the telomeres get a little shorter. Telomere length is like a biological clock corresponding to age. Telomeres also shorten as a result of exposure to stress. Scientists have uncovered links in adults between shorter telomeres and premature death, more frequent infections and chronic diseases.
Gotlib, the David Starr Jordan Professor and chair of the Department of Psychology, was surprised by the telomere shortening: "I did not think that these girls would have shorter telomeres than their low-risk counterparts – they're too young."
So which came first: stress, depression or premature aging? These otherwise healthy girls showed signs of stress and premature aging before any of them were old enough to develop depression.
Girls under stress
For this study, published recently in Molecular Psychiatry, the team recruited 10- to 14-year-old healthy girls with a family history of depression and compared them to healthy girls without that background.
The researchers measured the girls' response to stress tests, asking them to count backwards from 100 by 7's, and interviewing them about stressful situations. Before and after the test, the team measured the girls' cortisol levels. They also analyzed DNA samples for telomere length.
Before this study, "No one had examined telomere length in young children who are at risk for developing depression," Gotlib said.
What can a concerned parent or guardian do? Gotlib noted that other research shows exercise delays telomere shortening in adults, and he recommended that high-risk girls learn stress reduction techniques.