"Women who had a history of depression or who were currently depressed had about a 29% increased risk of stroke," says An Pan, PhD, research fellow at the Harvard School of Public Health. The increased risk remained even when risk factors such as cigarette smoking were taken into account.
Pan and his colleagues evaluated nearly 81,000 women, aged 54 to 79, who were enrolled in the Nurses' Health Study.
The research is in the journal Stroke.
About 795,000 Americans have a new or repeat stroke each year. Nearly 7% of U.S. adults experience depression in a given year. Women are 70% more likely than men to have depression at some point in their lives.
Depression and Stroke: Study Details
They asked the women if they were on antidepressant medication or had been in the past. Every two years, they asked if they had been diagnosed with depression now or in the past.
At the start of the study, 22% of the women reported current or past depression.
During the follow-up, 1,033 strokes occurred. When the researchers looked more closely, they found:
- Having a history of depression or current depression boosted risk by 29%. When they looked only at those in this group with current depression, risk increased by 41%.
- Having only a history of depression increased risk by 23%. That was not a risk increased enough to be significant.
- Current use of antidepressants boosted risk by 39% in women diagnosed with depression who were also found to be depressed on the mental health index.
However, Pan says the use of antidepressants is not thought to be linked with stroke risk. "The medication use could be a marker for depression severity." The most depressed were probably most likely to be on the medicine.
The study was funded by the National Heart, Lung, Blood Institute.
Depression and Stroke: Explaining the Link
Depression has been linked with heart disease risk. However, studies about depression and stroke are fewer and more recent.
Pan cannot explain the link, but speculates about possibilities. Depression may increase inflammation in the body, in turn increasing the risk of stroke. The women with depression, he says, were also more likely to be overweight, to smoke, and to be sedentary. Even though they took those risks into account, they might still contribute.
Depression and Stroke: Perspective
"This confirms an important association of depression with stroke," says Ralph Sacco, MD, chair of neurology at the University of Miami Miller School of Medicine and immediate past president of the American Heart Association.
"This study is large, well-conducted, and looked at not just depressive symptoms but the diagnosis of depression and taking of medication," he tells WebMD. He reviewed the study findings but was not involved in the research.
Although the researchers accounted for such risk factors as high blood pressure and cigarette smoking when they computed stroke risk, he says those factors may still be helping to drive the link.
The take-home message, he says, is to realize that depression affects far more than mental health. "We need to be recognizing depressive symptoms and doing something about it. Often people ignore depression and do not get it properly treated.
"If you are depressed, make sure you get the help you need," he says. Treatment may include medication, counseling, or both.