Lead author Darby E. Saxbe, a University of California at Los Angeles graduate student and Rena Repetti, a UCLA professor, said long-term elevated cortisol levels have been associated with depression, burnout, chronic fatigue syndrome, relationship problems, poor social adjustment and possibly cancer.

The researchers asked 60 middle-class parents to complete a standardized test of marital satisfaction and for two days the subjects tracked their work stress. Four times a day, the UCLA team collected saliva samples to detect cortisol concentrations.

Cortisol levels start high in the morning and decline during the day -- with intermittent rises as stressors arouse the adrenal gland. The slope of the hormone's daily decline is linked to well-being and better health.

The study, published in Health Psychology, found women in happy marriages enjoyed stronger cortisol declines than women in less blissful unions, but there was no difference in the men.

Women coming home from work may have to enter into another stressful routine and perhaps the happily married women share household duties more equally, resulting in their lower cortisol levels, Repetti said.