ORLANDO (USA TODAY) -- Good times with a mate improve health for both sexes, but a "nesting" hormone might give women's hearts even more benefit during brief episodes of warm contact with loved ones, a psychologist reported over the weekend.

Dubbed the "tend and befriend" hormone, oxytocin has attracted great interest since scientists found a few years ago that women under stress churn out more of it than men do, and oxytocin might prompt them to seek to comfort and nurture others. Testosterone appears to blunt the social bonding effect of oxytocin, which is a calming hormone. It stimulates milk release during breast feeding and is released in men and women during orgasm.

In the new study of 76 adults, all married or in long-term live-in relationships, partners who were happy together had significantly higher levels of oxytocin than unhappy couples, says psychologist Karen Grewen of the University of North Carolina-Chapel Hill. She reported her findings with colleague Kathleen Light at the American Psychosomatic Society meeting.

They asked each couple to talk privately for five minutes about a situation that brought them closer, then to view a romantic video and hug each other. During these warm exchanges, women's bodies reacted differently from men's, regardless of how happy they were with partners: Their oxytocin levels rose significantly more than men's and their blood pressure dropped. Women's surge in oxytocin also correlated with lower levels of the stress hormone norepinephrine. Oxytocin may trigger changes that protect women's hearts, Grewen says.

"It makes sense in evolution. Yes, you needed the testosterone -- someone to go out and kill the animals. But you needed a healthy person to stay and care for the kids too." She says more studies will be needed to confirm the findings.

There's evidence women suffer more stress than men from marital conflicts, "so this perhaps shows the positive side, that they're buffered more by happy contacts," says University of Toronto psychiatrist Brian Baker, who studies how marriage affects men's hearts.

Male heart patients with good marriages stay healthier than do those living with conflict, he says. "There are definite gender differences, but gender doesn't tell the whole story."

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