(CNN) New research reveals that the effects of PTSD can go beyond the mind -- and put women's hearts and brains at risk.

Post-traumatic stress disorder can wreak havoc on a person's ability to deal with small disturbances, such as a loud noise or an upsetting story in the news, and it can keep them from getting good sleep. In addition to these problems, and perhaps because of them, PTSD might also increase women's risk of heart attack and stroke, according to new research.

Researchers looked at nearly 55,000 women in the Nurses' Health Study II , a long-term study of young women that began in 1989. In 2008, the researchers asked the women to fill out surveys about traumatic events they had experienced in the last 20 years, including physical assault or a natural disaster as well as whether they had PTSD symptoms such as recurring thoughts about the event.

The researchers found that women who were exposed to a trauma and had at least four PTSD symptoms were 60% more likely to have a heart attack or stroke than women who reported having no trauma.

"This study raises awareness that the effects of PTSD don't just stop in the head and that they have more holistic consequences for health," said Jennifer A. Sumner, a clinical psychologist at the Columbia University Mailman School of Public Health. Sumner is lead author of the study , which was published Monday in Circulation, the journal of the American Heart Association.

"Our hope is that providers and patients (with PTSD) can be aware of this link and monitor cardiovascular health and try to engage in prevention efforts," Sumner said.

Previous research has reported links between PTSD and heart attacks as well as other types of heart disease, primarily in male war veterans . Sumner and her colleagues were interested in studying the connection in women, who are at higher risk of PTSD. (Ten percent of women have PTSD in their lifetimes compared with 5% of men.)

The current study found that even women who experienced a trauma, but did not report having any PTSD symptoms , were at 45% higher risk of heart attack and stroke than their trauma-free peers.

"That was somewhat surprising to us, although it's not too inconsistent with other findings," Sumner said. People who experienced trauma could have ramped up stress levels, such as higher levels of the stress hormone cortisol , which has been associated with heart attack risk, without being aware of it, she added.

However, women who were exposed to trauma and reported having only between one and three PTSD symptoms did not have an increase in heart attack or stroke risk, in contrast to women who experienced trauma and had either no PTSD symptoms, or at least four.

It might be too early to get a full picture of the heart attack and stroke risk in this study because the women, now between 44 and 62, are largely still too young to have these diseases, Sumner said. The researchers are following the women, and will see if those who reported having between one and three PTSD symptoms end up being at increased risk as well.

Part of the reason that women in this study were at greater risk of heart disease appeared to be their lifestyles. The researchers found that women who lived through a traumatic event, and had either zero or four or more PTSD symptoms, were more likely to engage in unhealthy behaviors, such as smoking and sedentary lifestyles.

In fact, about half of the increase in heart attack and stroke risk among the women who had at least four PTSD symptoms could be attributed to these behaviors. Among the women who had experienced trauma and no PTSD symptoms, these behaviors accounted for 14% of their risk.

Although there have been other studies looking at PTSD and heart disease risk, "this (study) is big because it's a very large sample, and if you've got thousands of people, it really drives the point home," said Dr. Una McCann, professor of psychiatry and behavioral sciences at Johns Hopkins University School of Medicine.

There is good evidence that use of alcohol tobacco and unhealthy behaviors, which can themselves increase heart disease risk, are more common in people with PTSD, McCann said. "But even on its own, PTSD can probably increase the risk," she said.

People with PTSD are in a constant state of hyper-awareness of their environment, which drives up their heart rates, McCann said. "Constantly having your heart on overdrive, it's not hard to figure out why that might cause heart attack and stroke," McCann said.

People with PTSD might also have trouble sleeping, partly because of nightmares. Sleep disorders, such as sleep apnea, are generally considered risk factors for heart disease, McCann said.

There's also a troubling relationship between PTSD and heart disease. Experiencing a heart attack, like other serious and unexpected illnesses, has been found to put people at greater risk of experiencing PTSD.

Fortunately, PTSD can be "cured," often with a combination of antidepressants, the drug prazosin, which curbs the release of adrenaline, and therapy, McCann said. By improving PTSD, these treatments can probably also lower the risk of heart attack and stroke, she added.