Veterans with post-traumatic stress disorder (PTSD) may also have damaged blood vessels that increase their risk for heart attacks and strokes, a U.S. study suggests.

In a test, researchers found that the blood vessels of vets with PTSD dilated less when they should have, compared to the vessels of vets without the mental health condition.

That indicates their blood vessels also may not be able to expand when necessary to increase blood flow in response to activities like intense exercise or to maintain circulation when fatty deposits and other debris clog artery walls. When blood flow is restricted, they would be more susceptible to heart attacks or strokes, particularly if they also have other risk factors like high cholesterol, hypertension or diabetes, researchers say.

Scientists aren't exactly sure how PTSD might affect the flexibility of blood vessels. But it's possible stress harms the inner lining of the vessels through changes in hormones or inflammation, said lead study author Dr. Marlene Grenon of the University of California, San Francisco.

"It is very likely that this would also happen in non-veterans who suffer from PTSD or chronic stress," Grenon said by email.

To explore the connection between PTSD and blood vessel health, Grenon and colleagues tested how well veterans' arteries relaxed and expanded when a blood pressure cuff tightened on their arms.

The experiment included 67 veterans with PTSD and 147 veterans without the condition. Most of the participants were men, and they were around 69 years old on average.

With PTSD, veterans' blood vessels expanded 5.8 percent on average in response to the tightening blood pressure cuff, compared with 7.5 percent without the condition. This indicates a less healthy response in the blood vessel lining with PTSD.

Aside from PTSD, veterans also experienced less blood vessel expansion if they were older or had high blood pressure or impaired kidney function, which might be related to diabetes.

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The veterans with PTSD were less likely than the others in the study to be taking drugs to manage their blood pressure.

Even after adjusting for these other health problems and differences in medication use, PTSD was still strongly associated with blood vessels that were less able to dilate, researchers report in the Journal of the American Heart Association.

The study was observational, and can't prove that PTSD causes blood vessel damage or leads directly to heart attacks and strokes, the authors note. It's also possible that depression, which is common among veterans with PTSD, could influence blood vessel health.

Even so, the findings suggest it makes sense to screen for cardiovascular risk factors when patients suffer from PTSD, said Kim Smolderen, a researcher at Ghent University in Belgium and Saint Luke's Mid America Heart Institute in Kansas City, Missouri.

There are good treatment options for PTSD including interventions like cognitive behavioral therapy, but these patients should also be screened for other mental health problems such as depression and anxiety, Smolderen, who wasn't involved in the study, said by email. Other therapy programs can also help patients manage day-to-day stress.

"Some of these programs have been shown to improve blood pressure levels," Smolderen said. "Whether or not the blood vessel health would directly be impacted by these programs, however, will need further investigation."