Two years later the research team used an optimism scale to analyze the association between optimism and stroke, taking into account other factors such as chronic illness, blood pressure, smoking, alcohol use and physical activity. The team found that the most optimistic participants were strikingly less likely to have suffered a stroke than the least optimistic.

Optimism, the researchers explain, is the expectation that more good than bad will come your way in the future. They note that optimism may protect people because those with a positive outlook make better choices such as eating well and exercising. "Optimistic people act in healthier ways," says Park.

But the effect of optimism may be more than simply looking at the world through rose-colored glasses. It may turn out that being an optimist has a biological influence. "That seems to be where some of the research is heading," says researcher Eric Kim, a study coauthor. "After all, depression and anxiety have a direct negative impact on the body, so theoretically why wouldn't factors such as optimism have a positive impact?"

"I'm not at all surprised that being optimistic is associated with health benefits," says neurologist Larry Goldstein, M.D., director of the Duke University Stroke Center, who was not involved in the study. "We know from many other studies that patients' attitudes can be incredibly powerful." But, Goldstein cautions, the study does not show that optimism causes lower stroke risk, simply that the two are associated. Optimism may be a marker for other behaviors or issues that weren't measured. "Still," he continues, "having a positive attitude certainly can't hurt."

The study was published in the July 21 online issue of Stroke: Journal of the American Heart Association.

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Nissa Simon writes about health and science in New Haven, Conn.