08/11/2011 04:19 pm ET | Updated Oct 11, 2011

Depression Increases Stroke Risk In Women, New Research Suggests

Depression does more than take a mental toll on people, leading to possible physical complications such as obesity and cardiovascular disease. Now, new research suggests that women of a certain age who have a history of depression may also have a 30 percent increased risk of stroke -- the third leading cause of death in the U.S.

Researchers from Harvard University used data from more than 80,000 middle-aged and elderly women (with an average age of 66) who participated in the Nurses' Health Study, one of the longest ongoing studies examining women's health in the U.S. They found that a history of depression substantially increased stroke risk, even after taking into account other risk factors for stroke.

Antidepressant medication also appears to play a role in stroke risk. Its use was associated with an increased risk of nearly 40 percent in women who had a history of depression, and an increased risk of almost 30 percent among women who had taken the medication, but had not necessarily been diagnosed with depression. (Depression medications are increasingly given for off-label use by patients with no mental health diagnosis; they are now the third most commonly prescribed class of drugs in the U.S.)

"At this point, we do not know whether it is the underlying depression or depressive symptoms that increase the risk of stroke, or the medications themselves," said An Pan, Ph.D, the study's lead author and a research fellow in the Department of Nutrition at the Harvard School of Public Health.

But the Harvard researchers did suggest several possibilities as to why depression and antidepressant use may up the risk of stroke in women.

Depression, they wrote, can cause certain physiological and hormonal changes in the body that in turn increase stroke risk. It is also sometimes tied to other factors that are known to raise stroke risk, including bad diet, smoking, lack of activity and a failure to take prescribed medications.

"Observational studies do suggest a link between both depression and [antidepressant medication] use and an increased risk of stroke," said John Lynch, a doctor of osteopathic medicine and a staff clinician with the NIH's National Institute of Neurological Disorders and Stroke, who was not associated with the research. The study received some support from NIH grants.

"Depression may be contributing to increased risk through a number of mechanisms, including brain hormone pathways, or an increased prevalence of poor health behaviors or medical disorders associated with stroke in depressed individuals," he added.

On the antidepressant front, the Harvard researchers cited previous studies that have found antidepressants can increase weight gain, inflammation, hypertension and abnormal bleeding -- all of which can lead to an elevated risk for stroke. They cautioned, however, that some earlier studies have found no association between the drugs and increased stroke risk. Indeed, Lynch said that previous observational studies have yielded "mixed results."

Which means, according to the authors of the Harvard study -- published in the American Heart Association's journal Stroke -- that women should not stop taking their antidepressant medications.

"This study does not recommend that people with depression withdraw their current medication treatment," Pan said. "However, physicians need to monitor the potential metabolic changes with antidepressant medication."