Research shows that depression in older women can have a deadly, often-overlooked symptom—an increased risk for stroke.

Harvard University researchers published a study in the journal Stroke indicating that elderly women who are depressed are more likely to have a stroke than their happier counterparts, reported.

Researchers examined the health data of over 80,000 women who participated in the Nurses' Health Study. Ranging in age between 54 and 79 years old, the women in the six-year study had no previous instance of stroke.

They found that the women who had been depressed at some point in their lives had a 29% increased risk of stroke. Those on medication for depression were 39% more likely to have a stroke.

Though the risk for stroke was higher among those women taking antidepressants, the researchers were not sure whether there is a causal link. Women who take medication to relieve intense depression may have a higher stroke risk because their disorder may be at a more advanced stage than someone who does not need medication.

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Strokes are also more likely to strike depressed women because their disease makes them less likely to take proper care of themselves by eating a healthy diet and getting regular exercise and the right amount of sleep.

Although elderly people sometimes feel blue, depression is not a normal part of aging, according to the National Institute of Mental Health.

If a senior begins to exhibit symptoms of depression for the first time, it may be a sign something is wrong physically. For example, vascular depression can occur when a person's brain is not getting enough blood. This condition can also be a harbinger of stroke.