Younger women suffering from heart disease are generally more affected by mental stress than their male counterparts, a study has found.

Psychological stress, which regular medical tests for a heart patient won't pick up, could be a factor in why women diagnosed with heart disease are more prone to suffering fatal heart attacks than are men who have heart disease, researchers say.

"Women who develop heart disease at a younger age make up a special high-risk group because they are disproportionally vulnerable to emotional stress," says study leader Dr. Viola Vaccarino of Emory University in Atlanta.

Young women with a stable heart condition are more likely than men to experience reduced blood flow to the heart if they're subjected to emotional stress, but not physical stress, the researchers said at the American Heart Association's Scientific Sessions 2014.

"There's a very interesting paradox concerning young women and chronic heart disease," says Vaccarino, explaining that despite having fewer risk factors for heart disease, they "have higher mortality and complication rates after heart attacks compared with men of the same age."

In their study, the researchers monitored the hearts of 534 patients ages 38 to 79 who had coronary heart disease, while they underwent both a mental stress test and a conventional physical stress test.

They scanned for signs of reduced blood flow to the heart muscle, a common problem with people suffering from coronary disease that can trigger a heart attack.

"Dramatic differences" in the scans were seen between men and women during the mental stress test, particularly in younger people, Vaccarino said.

In women under 55, mental stress caused a decrease in blood flow three times as great as in men in the same age range, the researchers said.

Women of that age bracket often face significant mental stress in their daily life while managing, work, childcare and in many cases the burden of caring for aging parents, Vaccarino pointed out.

Women are also known to be vulnerable to the effect depression can have on heart health, she added.

The significance of psychological stress and its impact on younger and middle-age women suffering from heart disease should not be underestimated, and doctors should "ask the questions about psychological stress that often don't get asked," she urged.

"If they note that their patient is under psychological stress or is depressed, they should advise the woman to get relevant help or support from mental health providers, stress reduction programs or other means."