Rexrode and her co-authors could not explain the mechanism linking depression and strokes, but suggested that depression might increase inflammation, which is known to damage blood vessels in the heart and brain. Depression also can alter neurological functions and the body's response to stress, and may make blood more likely to clot.
"These findings confirm our own findings in the Women's Health Initiative which showed that depression is a risk factor for subsequent stroke," said Sylvia Wassertheil-Smoller, a co-author of a large 2009 study in Archives of Internal Medicine that found older women taking antidepressants had a small, but statistically significant increase in stroke risk.
Wassertheil-Smoller, a professor of epidemiology and public health at Albert Einstein College of Medicine in the Bronx, N.Y., agreed with the current study authors about the need to inform doctors about the risks and to conduct additional research. "Since mild or moderate depression is not usually screened for, or even given much attention by primary care physicians, it is important that they be alerted to this finding," she said. "The interesting question is whether depression is a subclinical manifestation of impending stroke or whether there is some causal pathway."