As if depression isn’t hard enough on the mind, the condition can also wreak havoc all over the body, increasing risk of health problems that at first don’t seem remotely connected to feeling low. Depressed people are at increased risk for type 2 diabetes and cardiovascular death, and according to a new study published Wednesday in the Journal of the American Heart Association, they’re also at greatly increased risk for stroke. Adults over age 50 who report persistent symptoms of depression have double the risk for stroke, the study finds—and that increase lingers even after they report feeling better.
The researchers analyzed data from more than 16,000 middle-aged adults ages 50 and older. Every two years from 1998-2010, the people in the study were asked about their history of stroke, stroke risk factors and symptoms of depression.
People who reported high symptoms of depression—three or more symptoms from an eight-item depression scale—for four consecutive years had about 114% higher risk of stroke compared to those who did not have symptoms of depression at either interview.
It remains unclear exactly how prolonged depressive symptoms lead to an increased stroke risk, but the elevated risk appears to stick around for a long time, even after depression goes away. People whose depressive symptoms had subsided at the second interview still had a 66% higher risk of stroke than those without symptoms.
"We do not know if, had we been able to examine individuals who had been symptom free for a longer time, stroke risk would have declined more," said study author Paola Gilsanz, a postdoctoral fellow at Harvard T.H. Chan School of Public Health, in an email. "To assess that, we really need a larger study."
Just as stroke risk was slow to subside, it was slow to take hold, too. People who had just begun developing depressive symptoms weren’t at higher stroke risk than those without symptoms. "We were surprised to see that changes in depressive symptoms seem to take more than two years to influence risk of stroke," Gilsanz said.
It’s difficult to say from this study whether treatment has mitigating effects, since the authors didn't specifically look at why people's symptoms went away. But even though the data suggest that getting rid of symptoms of depression might not immediately erase the increased risk for stroke, they emphasize the importance of early treatment.
"If our findings are replicated, they suggest depressive symptoms merit prompt attention soon after they begin, before they have time to substantially impact stroke risk," Gilsanz says. "We also recommend that people with depression also focus on keeping their overall stroke risk profile as healthy as possible, as we all should."