A new study suggests that there may be a link between Post-Traumatic Stress Disorder (PTSD) and heart disease.

In a study of more than 8,000 veterans living in Hawaii and the Pacific Islands, those with posttraumatic stress disorder had a nearly 50 percent greater risk of developing heart failure over about a seven-year follow-up period, compared with their non-PTSD peers.

Although the study adds to a growing body of evidence linking PTSD and heart disease, but it doesn't show a clear cause-and-effect relationship.

"There are many theories as to how exactly PTSD contributes to heart disease," Dr. Alyssa Mansfield, one of the study authors, said in a statement. "Overall, the evidence to date seems to point in the direction of a causal relationship."

For the study, researchers tracked more than 8,000 veterans who had been outpatients in the VA Pacific Islands system. The researchers followed them an average of just over seven years. Those with a PTSD diagnosis were 47 percent more likely to develop heart failure during the follow-up period. The researchers controlled for differences between the groups in health and demographic factors.

Out of the total study group, about 21 percent were diagnosed with PTSD. Of the total 371 cases of heart failure during the study, 287 occurred among those with PTSD, whereas only 84 cases occurred among the group without PTSD.

Combat service, whether or not it led to a full-blown PTSD diagnosis, was itself a strong predictor of heart failure. Those Veterans with combat experience were about five times more likely to develop heart failure during the study period, compared with those who had not seen combat. Other predictors of heart failure were advanced age, diabetes, high blood pressure, and overweight or obesity.

The findings are detailed in the American Journal of Public Health.