Women and Stress
By: Judy Foreman
08/13/02

Do men and women handle stress differently? Or, to put it more provocatively, do women have a built-in hormonal advantage when it comes to dealing with chronic stress?

That’s the (highly loaded) question at the heart of a fascinating body of research that’s got the Net humming, with enthusiastic emails flying from woman to woman.

The case for this feminist theory of stress management is circumstantial  – built largely on inferences from animal studies and, at some points, frank leaps of faith. Still, the hypothesis has intuitive appeal, at least to women, so it’s worth exploring.

For decades, scientists who study the body’s physiological response to stress have focused on the “fight or flight” model. This view says that when an animal perceives danger, a number of hormones kick into action (among them, cortisol, ACTH, CRH, vasopressin and others). These hormones rev up heart rate and blood pressure, get sugar to the muscles and generally speed things up, the better to fight predators or get out of harm’s way, fast.

And there is absolutely no question that both males and females have – and need – this system.

But this view of stress is both male-biased and incomplete, say a number of researchers, most notably Shelley E. Taylor, a professor of psychology at the University of California at Los Angeles.

Taylor’s theory, based on more than 200 studies by other people, mostly biologists and psychologists, is that women have a powerful system for fighting stress that’s based in part on a hormone called oxytocin.

Granted, there’s no clear evidence that women on average actually have more oxytocin in their bloodstreams than men. But they do have more of another hormone, estrogen, which does boost the effectiveness of whatever oxytocin is around.

Oxytocin, which some dub the “cuddling” or social attachment hormone, is best known as the hormone produced during childbirth and lactation and during orgasm, in both sexes. But it’s also secreted during other forms of pleasant touch, such as massage, and has been shown to stimulate bonding in animals, most notably prairie voles and sheep.

Even more intriguing, there’s evidence from the laboratory of Kerstin Uvnas-Moberg at the Karolinska Institute in Stockholm and elsewhere that oxytocin may act as a genuine “antistress” hormone.

For instance, the Karolinska group reported in 1998 that daily oxytocin injections, into both male and female rats, decreased blood pressure and the stress hormone, cortisol, and promoted weight gain and wound healing. The group has also shown that injections of oxytocin in rats enhanced sedation and relaxation and reduced fearfulness.

To Taylor and her colleagues, the thrust of this evidence suggests that women may be programmed by evolution to deal with stress, not just in the “male” way, by fighting aggressors or running away, but also by “tending and befriending,” that is, turning to each other for moral support and nurturing the young.

In other words, “there appears to be a counter-regulatory system that may operate more strongly in females than males, that leads to engagement of oxytocin and social contact,” which in turn may reduce stress, says Taylor, author of the book, “The Tending Instinct.”

“If we want to get a complete picture of how people manage stress, we need to look at both men and women,” she adds. “Historically, researchers have looked mostly at men.” Indeed, prior to 1995, women constituted only 17 percent of studies of the hormonal responses to stress. Things have gotten somewhat better since then, she says, but of nearly 15,000 people in 200 stress studies between 1985 and 2000, only 34 percent were female.

What, then, is really known about oxytocin? Quite a bit.

First, it’s a tiny molecule of only nine amino acids that is made in a part of the brain called the hypothalamus. It works closely with a related molecule, vasopressin, which is carried on the same chromosome as oxytocin and is so similar that the two chemicals fit into each other’s receptors in the brain, notes Sue Carter, a behavioral neuroendocrinologist at the University of Illinois in Chicago.

But while oxytocin, which acts in tandem with estrogen, often has calming effects, vasopressin, which acts in tandem with the male hormone, testosterone, can act as a stress response enhancer, among other things, raising blood pressure.

In most species, says Carter, male brains contain more vasopressin than female brains, especially in an area called the amygdala, a fear processing center. Vasopressin has also been linked to increased aggression and male territoriality.

Put another way, oxytocin “is associated with typically female behaviors, such as childbirth and nurturing the young, whereas vasopressin is associated with male behaviors, such as territorial aggression,” writes Dr. Norman Rosenthal, clinical professor of psychiatry at Georgetown University in his new book, “The Emotional Revolution.”

The most intriguing feature of oxytocin is that it seems to act as both a cause of bonding between animals and a result of it, suggesting that perhaps through bonding behavior, it can be a stress reducer.

For instance, a number of studies have shown that oxytocin promotes bonding in animals: between mothers and babies, and between adults. In prairie voles, Carter’s studies show, injections of oxytocin lead to increased bonding. And when stressed, Carter has found, both male and female voles choose to bond - with females.

 “Many things stimulate production of oxytocin, including breast stimulation, orgasm or even contact with a friendly companion,” says Carter. “All these are  known to release oxytocin, which may help damp down the body’s reactions to stressful experiences, in men as well as women.”

Several studies, for instance, have suggested that women who nurse their babies have lower anxiety compared to bottle-feeding mothers and that lactating rats exhibit less fear.

In one 1995 study, for instance, Carter and Dr. Margaret Altemus, a psychiatrist at Weill Medical College, Cornell University, asked about 20 new mothers to undergo an exercise stress test – running on a treadmill. About half the women were nursing and half were bottle-feeding. The women who were bottle-feeding showed steeper increases in stress hormones than the nursing mothers. Other studies, notes Altemus, have suggested that panic disorder is relieved during pregnancy and lactation.

In other words,  “there may be something going on in a woman’s nervous system that may protect her against stress, at least transiently,” says Carter. And because any kind of positive social experience has the potential to trigger release of oxytocin in both men and women, she adds, men as well as women can  benefit from positive emotional contact with other people.

Beyond oxytocin, there are other chemical clues to differences in the ways in which women and men may handle stress.

At Ohio State University, Janice Kiecolt-Glaser, professor of psychiatry at Ohio State University  and her husband, Ronald Glaser, an immunologist, have studied hormonal and immunological responses to stress and found some striking gender differences.

In one experiment, the Ohio team asked 90 young, happy, newly-wed couples to spend 24 hours, including a night’s sleep, in the hospital lab. “They were in absolutely pristine mental and physical health,” says Kiecolt-Glaser. The researchers placed a catheter in each subject’s arm so that blood could be drawn every hour to test for hormone levels and various aspects of immune function.

Early in the stay, each couple was asked to spend 30 minutes discussing an area of disagreement. This conflict was recorded on videotapes that were later scored by trained observers, both male and female, for evidence of negative behavior such as hostility, sarcasm, put downs, etc.

The results were stunning:  Marital strife was much tougher on women than men. The women showed a faster and more enduring response to hostility, says Kiecolt-Glaser, noting that women’s stress hormones (particularly epinephrine, norepinephrine and ACTH) rose more sharply and stayed up longer than men’s. Women also showed a lowering of certain aspects of immune function.

In a follow-up study, the Ohio team found that women whose stress hormones had risen the highest during the earlier phase of the study were the most likely to get divorced.

 “Women show greater sensitivity to negative marital interactions than men,” says Kiecolt-Glaser. And this can’t be chalked up to over-reacting, or to some female hypersensitivity to stress in general because in other situations designed to induce stress in the lab, such as being asked to perform mental arithmetic, men show larger increases in stress than women.  

In other words, in a marriage, Kiecolt-Glaser says, women are actually more accurate judges of what’s going on emotionally. Indeed, when the outside reviewers rated the videotapes of the couples’ interactions, their assessment of hostility and negative behavior correlated with the women’s. Women simply experience a bigger stress response to men’s sarcasm and hostility than men do to women’s, she says.

The bottom line? If you feel stress in an interpersonal relationship, you’re probably right that the stressors are truly there. If you do feel stressed out, call a friend. If you don’t have a friend, make one, or more. And if all else fails, snuggle up with a prairie vole.

Judy Foreman is  Lecturer on Medicine at Harvard Medical School and an affiliated  scholar  at the Women’s Studies Research Center  at Brandeis University.. Her column appears every other week. Past columns are available on www.myhealthsense.com.

SIDEBAR

Do Women Have More Stress than Men?

At least in terms of behavior and feelings – as opposed to physiological measures of oxytocin and other hormones – there are clear differences in the ways men and women experience stress.

For one thing, women seem to have more of it, even though they outlive men, says Ronald Kessler, a sociologist and health care policy professor at Harvard Medical School.  

In one 1998 study done with colleagues at the University of Arizona, Kessler had men and women keep daily mood diaries for a week. “There were large sex differences,” he says. Men and women were equally good at getting rid of minor “spells of depression,” says Kessler, but “women have more bad stuff going on.”

“What really gets to people is the little crap,” says Kessler, “the daily hassles,” which women may have more of because they are often the ones who take responsibility for coordinating family and work schedules. “It’s the coordination that kills you, and when something gives, it’s the woman who fills in the gap.”

And while women often do relieve their own stress by turning to each other, the fact that women also often have more people in their lives to care –and worry – about may actually increase stress, says Kessler. “Men and women have the same emotional reactions” when something bad happens to people close to them, he says, but women often have more people in those networks, a phenomenon he calls the “cost of caring.”

Psychologist Alice Domar at the Mind/Body Medical  Institute at Beth Israel Deaconess Medical Center in Boston agrees that data clearly show that women are more stressed day to day than men, and it’s not, as was once thought, because they ruminate more.

“Men worry about three things: their immediate family, their job and money,” she says. “Women worry on a daily basis about up to 12 things – their immediate family, their job, money, their extended family, their friends, their kids’ friends, the way the house looks, their weight, the dog, etc.”

That same gender breakdown seems to occur in one of life’s most stressful situations, being diagnosed with cancer, says Barrie Cassileth, a psychologist and medical sociologist who runs the integrative medicine service at Memorial Sloan-Kettering Cancer Center in New York.

When first diagnosed with cancer, “men and women do respond very differently,” she says. “Women always talk…and women gain as much from giving as from receiving support from others. Women have such a nurturing instinct that even when facing harsh realities, they do reach out to others.”  

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