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Researchers figured something similar had to be happening in burnout victims. But rather than finding a prominent cortisol peak, investigators discovered a shallow bump in the morning followed by a low, flattened level throughout the day. Intriguingly, such blunted cortisol responses are also common among Holocaust survivors, rape victims and soldiers suffering from PTSD. The difference seems to be that people with PTSD are much more sensitive to cortisol at even these low levels than those with burnout. "We used to blame everything on high cortisol," says Rachel Yehuda, a neurochemist and PTSD expert at the Mount Sinai School of Medicine in New York City. "Now we can blame things on low cortisol as well."
STRESS CAN AGE YOU BEFORE YOUR TIME
SCIENTISTS HAVE LONG SUSPECTED THAT unremitting stress does damage to the immune system, but they weren't sure how. Then two years ago, researchers at the University of California, San Francisco, looked at white blood cells from a group of mothers whose children suffered from chronic disorders like autism or cerebral palsy. The investigators found clear signs of accelerated aging in those study subjects who had cared the longest for children with disabilities or who reported the least control over their lives.
The changes took place in microscopic structures called telomeres, which are often compared to the plastic wrappers on the ends of shoelaces and which keep chromosomes from shredding. As a general rule, the youngest cells boast the longest telomeres. But telomeres in the more stressed-out moms were significantly shorter than those of their counterparts, making them, from a genetic point of view, anywhere from nine to 17 years older than their chronological age.
STRESS IS NOT AN EQUAL-OPPORTUNITY EMPLOYER
IN 1995, IN A NOW CLASSIC EXPERIMENT, SCIENTISTS AT THE University of Trier in Germany subjected 20 male volunteers to a situation guaranteed to raise their stress levels: participating in a mock job interview and solving arithmetic problems in front of strangers who corrected them if they made mistakes. As expected, each subject's cortisol level rose at first. But by the second day of the trial, most of the men's cortisol levels did not jump significantly. Experience had taught them that the situation wasn't that bad. Seven of the men, however, exhibited cortisol spikes every bit as high on the fourth day as the first. Only by the fifth day did their stress reaction begin to disappear.
More recently, researchers have found that subjects with low self-esteem are more vulnerable to stress. Jens Pruessner at McGill University in Montreal believes that the hippocampus, a finger-size structure located deep in the brain, is at least partially responsible. It turns out that the hippocampus, which helps you form new memories and retrieve old ones, is particularly sensitive to the amount of cortisol flooding your cerebrum. So when cortisol levels begin to rise, the hippocampus sends a set of signals that help shut down the cortisol cascade.