Women with a history of depression may have an increased risk of stroke, a new study suggests.

Use of antidepressants was tied to 1.29 times the risk of stroke compared with women who said they were never diagnosed with the condition, researchers reported in Thursday's online issue of the journal Stroke: Journal of the American Heart Association.

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Stroke patients may have difficulty moving. Depression could be a risk factor for stroke, a study of women suggests. ((Duke University/Associated Press))

More than 80,000 women with no history of stroke and an average age of 66 participated in the Nurses' Health Study

For the study, a team of public health investigators interviewed and assessed the women every year for six years. Participants' medical history was reviewed, and other risk factors such as smoking and physical activity were taken into account.

"Our study demonstrates that depression could be an independent risk factor for stroke," said An Pan, lead author of the study and a research scientist at the Harvard School of Public Health in Boston.

Participants reported their use of the medications every two years. Women who used antidepressant medication, particularly selective serotonin reuptake inhibitors such as Prozac and Zoloft, had 1.39 times the risk of stroke.

Taking antidepressants may be an indicator of depression severity, said Dr. Kathryn Rexrode, the study's senior author and a physician at Brigham and Women's Hospital in Boston.

"I don't think the medications themselves are the primary cause of the risk. This study does not suggest that people should stop their medications to reduce the risk of stroke," Rexrode advised.

Call for stroke prevention strategies

Depression may increase the risk of stroke in a variety of ways, but how isn't know. Possibilities include inflammation, which increases the risk of stroke as well as other conditions or underlying vascular disease in the brain, the researchers suggested.

"Whatever the mechanism, recognizing that depressed women may be at higher risk of stroke merits additional research into preventive strategies for this group," the study's authors concluded.

During the study, 1,033 strokes of various types were documented from self-reports. Another 221 fatal strokes were recorded. Researchers looked for medical records, autopsy reports or death certificates to try to confirm the deaths.

One of the drawbacks of the study is that the participants were mainly white registered nurses. The findings may not be true for other populations, the study's authors said.

Many Canadian doctors and health associations are now reviewing the findings.

"We don't necessarily know if it's what people are doing in their lives that corrupts the integrity of the body or whether depression itself kind of leads to shutdown of certain systems," said Dr. Zindel Segal, a psychologist at the Centre for Addiction and Mental Health in Toronto.

"I wouldn't be suprised if it is both."

The U.S. study is ongoing, and the research  team plans to keep following the women to better understand how depression and stroke may be related.

The study was funded by the U.S. National Institutes of Health, the National Heart, Lung and Blood Institute and the National Alliance for Research on Schizophrenia and Depression.

With files from CBC's Melanie Nagy