Depression and stroke: Analysis of studies finds a connect

By Dr. Ananya Mandal, MDSep 22 2011

A latest study shows that people who are depressed may be a little more likely than others to suffer a stroke down the road. Looking at 28 past studies, researchers estimated there would be 106 extra cases of stroke per 100,000 depressed people each year, 22 of them fatal.

As of now the researchers do not know how to account for the link - people who have the blues might smoke more and exercise less, for instance. Indeed, accounting for that did weaken the apparent association between depression and stroke, which kills about 137,000 Americans a year.

And there's a more troubling possibility, said An Pan, a researcher at Harvard School of Public Health in Boston who worked on the study. In an earlier study, he found depressed people who take antidepressants appeared to have an increased risk of stroke compared with depressed people who weren't on the drugs. “These medications could be one possible reason for the increased risk of stroke in depression and the majority of studies did not control for this,” he said. He stressed, however, that antidepressant use might also just be an indicator of severe depression, which might account for the extra risk. “The current data on whether medications have an independent role (in stroke) is not clear at this moment,” Pan said.

The findings, published in the Journal of the American Medical Association, are based on a total of more than 317,000 people followed for two to 29 years.

“We were not surprised by the results because previous studies, including our work in this area, have demonstrated that depression increases the risk of obesity, diabetes, and coronary heart disease,” said Pan. “Depression should be considered as an independent risk factor for the future risk of stroke.”

Stroke is a leading cause of death and permanent disability, with significant economic losses resulting from functional impairments, Dr. Pan pointed out. Depression is highly prevalent in the general population, and it is estimated that 5.8% of men and 9.5% of women will experience a depressive episode in a 12-month period. The lifetime incidence of depression has been estimated at more than 16% in the general population. The prevalence is thought to be even higher in people with comorbidities such as obesity, diabetes, and hypertension.

Given the high prevalence and incidence of depression and stroke in the general population, Dr. Pan said, the observed association between depression and stroke has clinical and public health importance. “More studies are needed to explore the underlying mechanisms and elucidate the causal pathways that link depression and stroke.”

Linda Williams, from the Indiana University School of Medicine in Indianapolis, pointed out the timing of depression in relation to stroke is a critical issue that has not been well studied. “Any depression recognized after a stroke has occurred is termed post-stroke depression, and whether the depressive symptoms predated the stroke is not ascertained.”

She points out that more work needs to be done in this area. “Because effective treatments exist but are likely underutilized for depression, this is an important example of an evidence-practice gap to which increased efforts to improve care should be made. Such efforts would likely improve not only patient symptoms but may also decrease stroke risk, influence stroke functional recovery, decrease mortality, and reduce post-stroke health care utilization.”

This study was supported by the National Institutes of Health.