Depression and heart disease seem to be linked, and now a new study shows that this link may be stronger in middle-age women than in men or older women.
Women in the study who were age 55 and younger and had moderate or severe depression were more likely to have coronary artery disease, and had more than twice the risk of having a heart attack or a stroke, or dying of a heart problem, during the three-year study than either men or older women who suffered from depression, the researchers said.
"Women in this age group are more likely to suffer from depression, so this may be one of the 'hidden' risk factors that explains why women die at a disproportionately higher rate than similarly aged men after a heart attack," said Dr. Amit Shah, assistant professor of epidemiology at Emory University in Atlanta and one of the study's authors.
In the study, researchers assessed depression symptoms in more than 3,000 people (34 percent of whom were women). All of the people in the study had either been diagnosed with heart disease or were suspected to have it, and were scheduled for coronary angiography, an X-ray that looks for problems in the arteries that supply blood to the heart.
The researchers adjusted for factors that could affect people's risk of heart disease, including race, high blood pressure, diabetes, history of stroke or heart disease, and smoking habits. [7 Ways Depression Differs in Men and Women]
The researchers found that women age 55 and younger with moderate or severe depression were 2.17 times more likely to suffer a heart attack, die of heart disease or require an artery-opening procedure during the follow-up period than were older women and men of a similar age who also suffered from depression.
The researchers also found that women in this age group who suffered from moderate or severe depression were 2.45 times as likely as older women and men of a similar age to die from any cause during the study period.
In men and older women, symptoms of depression were not linked with heart disease, the researchers said.
The study appears today (June 18) in the Journal of the American Heart Association.
Shah said that although it's unclear exactly how depression and heart problems may be linked, researchers do have ideas about why depression in younger women is linked to heart disease.
"One of the possibilities is that hormonal and/or neurological imbalances occurring in the brains of women who are moderately or severely depressed can have adverse effects on the cardiovascular system," he told Live Science. "The other possibility is inflammation, which has been measured at higher amounts in people with depression and is a core risk factor for heart disease. The question remains, which came first: the depression or the inflammation?"
Shah said that more clinical studies on inflammation and depression need to be conducted on middle-age women, to determine if medications that reduce inflammation might reduce depression as well.
Another possible underlying reason for the link, the study noted, is that women may respond physiologically to stress and depression differently than men do. For example, early-life trauma, which is a risk factor for depression, is known to worsen the body's normal chemical response to acute stress in young women. Over time, this may lead to obesity and certain metabolic abnormalities that are known risk factors for heart disease, the researchers said.
The findings in the new study indicate a need for more research on heart disease and psychosocial factors, particularly depression, in young women, Shah said.
"This population is often underrepresented in clinical studies of cardiovascular disease," he said. "Since heart disease is the most common cause of death in women, reducing depression in young women may have a significant impact on public health."