IN A NEW study, California scientists have identified the first direct link between emotional stress and cellular changes associated with premature aging.
Widely praised by other researchers, the study reinforces the popular belief that emotional stress may have serious medical consequences. It is also consistent with the idea that stress-reducing practices such as yoga, meditation, jogging or any version of the "relaxation response" may reduce the risk of certain diseases.
But before you stress out about the ill effects of stress, a few cautions. Many of the biochemical links between feeling stressed and getting sick are still unknown. And stress clearly doesn't cause everything.
"For a long time, people believed that stress caused cancer. It's not true," said psychologist Barrie Cassileth, chief of the integrative medicine service at Memorial Sloan-Kettering Cancer Institute in New York.
Several studies have looked at people who have lost a child, been in concentration camps or psychiatric wards or were prisoners of war -- and found no link between those stressful situations and cancer.
On the other hand, previous studies have shown that chronic stress is linked to a higher risk of heart attack, high blood pressure and insomnia, said Dr. Herbert Benson, president of the Mind / Body Medical Institute and an associate professor of medicine at Harvard Medical School. Stress is also associated with more intense hot flashes, a lower threshold for pain, and increased anxiety, depression, excessive anger and hostility.
That said, the new study is "a very important milestone" in mind-body research, said Bruce McEwen, director of neuroendocrinology at Rockefeller University in New York.
In a commentary accompanying the California paper in the Proceedings of the National Academy of Sciences, Robert Sapolsky of Stanford University wrote that the discovery is "remarkable" and "exciting" because it ties together an emotional state with fundamental cell biology.
In the study, researchers from the University of California, San Francisco followed 58 women ages 20 to 50. Thirty-nine of the women were taking care of a chronically ill child and the rest were raising healthy children. The sick children had been diagnosed between one and 12 years ago.
All the women were healthy, but in women who were more stressed, as gauged both by their subjective ratings of stress and by the duration of their caregiving, cells showed signs of premature aging. Their telomeres, tiny structures on the tips of chromosomes, were shriveling faster than normal. Like the tips of shoelaces, telomeres protect the ends of chromosomes; once telomeres get too short, a cell can no longer divide.
The longer a woman took care of a sick child, the shorter were the telomeres in her white blood cells, said lead author Elissa Epel, a UCSF psychologist. The women who felt most stressed also had lower levels of telomerase, an enzyme that restores telomere length. And they had greater "oxidative stress," a measure of damage done to cells by destructive forms of oxygen, noted Elizabeth Blackburn, a UCSF professor of biochemistry and biophysics and a co-author of the paper.
The women whose subjective ratings of stress were the highest had the equivalent of 10 years of extra aging in their immune cells, compared to women in both groups who rated their stress lower, said Epel.
"It's how you perceive stress that is important, not caregiving per se," she said, adding that the same external situation can produce different kinds of stress in different people.
With "threat stress," people feel that their very survival or self-esteem is in jeopardy, triggering feelings of anxiety and loss of control. Another person in the same situation might feel "challenge stress," seeing the situation as an opportunity to rise to the occasion.
One implication is that if you're in what you perceive to be an unpleasantly stressful situation, change the situation if you can. If you can see the situation in a less stressful light, that may help, too, though this can be hard to do.
The California study is actually the latest in a series of findings documenting a link between chronic emotional stress and disease or immune system disruption.
In one 1999 study, University of Pittsburgh researchers found that people who were taking care of an ill spouse and experiencing stress had a 63 percent higher risk of death over a four-year period than non-caregivers in the same study.
At Ohio State University, the husband-and-wife team of Janice Kiecolt-Glaser, a psychologist, and Ronald Glaser, an immunologist, have found that spouses who take care of partners with dementia have weakened immune systems.