Medical researchers have known for several years that there is some sort of link between long-term depression and an increased risk of stroke. But now scientists are finding that even after such depression eases, the risk of stroke can remain high.
"We thought that once people's depressive symptoms got better their stroke risk would go back down to the same as somebody who'd never been depressed," says epidemiologist Maria Glymour, who led the study when she was at Harvard's T.H. Chan School of Public Health. But that's not what her team found.
Even two years after their chronic depression lifted, Glymour says, a person's risk for stroke was 66 percent higher than it was for someone who had not experienced depression.
The study analyzed data across a dozen years for more than 16,000 adults, age 50 or older. Participants were asked to complete a survey every two years from 1998 to 2010 that asked, among other things, about their mood the previous week.
The questions, Glymour says, included whether "during the past week, they had often felt depressed; felt that everything they did was an effort; whether they had had restless sleep; they felt lonely; whether they couldn't 'get going'; whether they felt sad."
If people answered "yes" to three or more of these questions, the researchers counted them depressed. The scientists also kept track of whether participants had a stroke during the 12-year study period.
Now, Glymour expected people with long-term depression to have a higher risk of stroke. And they did — more than double the risk of those who weren't depressed. But she was not expecting stroke risk to continue as long as two years after the depression lifted.
Scientists don't yet know the mechanisms involved, she says — why depression would predispose someone to stroke. It could have something to do with the body's physical reaction to the psychological malady, Glymour says.
"Changes in immune function," she says, "[or] inflammatory response, nervous system functioning — all of these might influence blood pressure [or] cortisol levels and thereby increase your risk of stroke."
It's also possible, she says, that depression changes a person's behavior in ways that increase the risk of stroke. People may be more likely to smoke cigarettes or drink excessive amounts of alcohol when depressed, or find it harder to get exercise.
Glymour says the study's findings imply that the negative health effects of depression are likely cumulative over time — people whose diagnosis of depression was very recent were not more likely to have a stroke than people who never had symptoms.
That's one more reason why it's so very important to treat depression as soon as possible, she says. Dr. Renee Binder with the American Psychiatric Association agrees.
"There is no health without mental health," Binder says, adding that people should be routinely screened for depression and anxiety when they see their primary care provider.
The answers to just a few questions — such as whether patients feel sad many days of the week or get pleasure from everyday activities — can be clear warning signs that more extensive screening is needed, maybe including a referral to a mental health specialist.
The good news, Binder says, is that depression can be "extremely treatable" once it's addressed. A short course of psychotherapy or a short course of medication, she says, can quickly turn things around in many cases.
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STEVE INSKEEP, HOST:
And next we have an important reminder of how your mental health can affect your physical health. We knew there's a link between depression and the risk of stroke. Now research suggests that the risk of a stroke outlasts your depression. Even after you're feeling better, the risk stays high. That is the finding of the journal of the American Heart Association. NPR's Patti Neighmond reports.
PATTI NEIGHMOND, BYLINE: Researchers were surprised by the findings. Epidemiologist Maria Glymour headed the study at Harvard's T. H. Chan School of Public Health.
MARIA GLYMOUR: We thought that once people's depressive systems got better, their stroke risk would go back down to the same as somebody who'd never been depressed.
NEIGHMOND: But that's not what Glymour found.
GLYMOUR: We found that people who had depressive symptoms but then had gotten better and their depression had gone away still had an increased risk of stroke of 66 percent.
NEIGHMOND: Now, this was the case up to two years after people's depression went away. To figure out if people were depressed in the first place, researchers analyzed how more than 16,000 adults over 50 answered questions like these.
GLYMOUR: If during the past week they had often felt depressed or felt that everything they did was an effort, whether they had had restless sleep, whether they couldn't get going, they felt lonely, whether they enjoyed life, whether they felt sad.
NEIGHMOND: And if people said yes to three or more questions, they were considered depressed. Now, Glymour expected people with chronic depression to have a higher risk of stroke, and they did - more than double the risk of those who weren't depressed. But here's the mystery - scientists don't know how depression is linked to stroke. Glymour says it could have something to do with the body's physical reaction to depression.
GLYMOUR: Changes in immune function, changes in inflammatory response, changes the nervous system functioning, and all of these might influence hypertension, blood pressure, cortisol levels and thereby increase your risk of stroke.
NEIGHMOND: Or it could be that depression affects other important behaviors.
GLYMOUR: Because it's changing how people behave and making it harder to behave in healthy ways.
NEIGHMOND: For example, she says, depression may make it hard to get up and exercise. It may make people more likely to smoke cigarettes or drink too much, and it may make it difficult to manage other stroke risk factors like hypertension or diabetes. Glymour says the findings of her study suggest the negative health effects of depression can be cumulative over time, which is why she says it's so important to treat depression as soon as possible. Dr. Renee Binder with the American Psychiatric Association couldn't agree more.
RENEE BINDER: There is no health without mental health. When people come to their primary care physician, they should be screened for depression, for anxiety.
NEIGHMOND: Answers to just a few questions such as whether patients feel sad many days of the week or get pleasure from everyday activities can be clear warning signs that more extensive screening is needed and perhaps referral to an a mental health specialist. The good news, says Binder, depression is extremely treatable.
BINDER: When people are depressed and, depending on their particular symptoms, they are given a short course of psychotherapy or a short course of medications, they can do very, very well.
NEIGHMOND: And in fact, she says, up to 90 percent of patients with depression get better with treatment. In her study, researcher Maria Glymour found people recently diagnosed recently with depression were not at a higher risk of stroke, so early diagnosis and treatment, she says, can make all the difference in decreasing the risk of stroke. Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.