That's the suggestion from a new UCLA study that tracked levels of cortisol, a key stress hormone, among 30 Los Angeles married couples involved in one of our age's trickiest juggling acts — raising kids when both parents work full time.

"At least as far as women are concerned, being happily married appears to bolster physiological recovery from work," said Darby E. Saxbe, the study's lead author and a UCLA graduate student in clinical psychology. "After a tough day at the office, cortisol levels dropped further among happily married women than less happily married ones. Less happily married women also showed a flatter daily pattern of cortisol release, suggesting that they are rebounding less well from everyday stress."

Long-term elevated cortisol levels have been associated with a host of maladies, including depression, burnout, chronic fatigue syndrome, relationship problems, poor social adjustment and possibly even cancer.

"This is the first study to show that daily cortisol patterns are linked to marital satisfaction for women but not men," said co-author Rena Repetti, a UCLA professor in the department of psychology.

The findings, which are part of a larger study conducted by the UCLA–Sloan Center for the Everyday Lives of Families (CELF), appear in the January issue of Health Psychology, a peer-reviewed journal published by American Psychological Association. Adrienne Nishina, an assistant professor of human development at the University of California, Davis, was the study's third author.

CELF researchers asked the study's 60 middle-class parents to complete a standardized test of marital satisfaction. Twice during each of the three days over which the study was conducted, the parents also filled out a questionnaire while they were at work that asked how their workday was going and how busy they felt. At four intervals — early morning, late morning, afternoon and evening — the UCLA team collected saliva samples, which were then analyzed for cortisol concentrations.

Released by the adrenal glands under stressful conditions, cortisol is widely considered a reliable marker for an individual's response to — and recovery from — stress. Cortisol levels start high in the morning and steadily decline over the course of the day, with intermittent rises as stressors arouse the adrenal gland. The slope of the hormone's daily decline is believed to be correlated with well-being, with steeper declines reflective of better health and shallower declines predictive of health problems.

"Cortisol may by one of the routes by which repeated everyday stress translates into long-term mental and physical health problems," Repetti said.

Overall, women in happy marriages enjoyed stronger cortisol declines than their counterparts in less blissful unions, the UCLA team found. Men, no matter the quality of their marriage, showed an exaggerated cortisol decrease after busier days. However, only happily married women appeared to enjoy this benefit; unhappily married women did not show the exaggerated drop-off in cortisol after a busy day.

The investigators said additional research is needed to understand precisely how marital satisfaction influences the body's stress response process. But they believe that a natural tendency to socially withdraw after a stressful day may help explain why men and happily married women showed the exaggerated decline in cortisol after busier days at work while unhappily married women did not.

"They're coming home from a busy day and instead of having some time to unwind and relax and have a spouse picking up the load of setting the table, getting dinner going, signing forms for the kids, these women may have to immediately to launch back into another stressful routine," Repetti said. "Perhaps in happily married couples the demands of domestic life are being shared more equitably between men and women, or at least that may be the case when wives return home from a demanding day at work."

Past research has looked at the effects of marital satisfaction on cortisol levels, but the CELF study is the first to look at the relationship outside of the laboratory separately in men and women. Most researchers in the past have aroused cortisol responses by subjecting participants to such stressors as public speaking or electric shock. The CELF study, on the other hand, tracked real-life families as they went through their actual daily routines.

"Past research has found that men appear to get a health and longevity boost from marriage, while for women, being married is only beneficial insofar as the marriage is high-quality," Repetti said. "This study is the first to point to daily cortisol fluctuations as a specific pathway through which marital quality affects health for women but not men."

"It may be that a chronically unhappy marriage creates multiple occasions everyday when the wife needs to mount a stress response, putting her cortisol levels on a kind of roller coaster ride," Repetti said. "The system is under more wear and tear. It's like driving a car in traffic conditions that are constantly stop and go. You need to repeatedly step on the gas and apply the brakes, step on the gas, apply the breaks. Over time, you create a less reliable system. You don't stop and re-accelerate as quickly. You don't recover as quickly."