Adding to evidence that mental health conditions may affect heart health, a new study finds that veterans with anxiety disorders have an increased risk of heart attack.

Using medical records from nearly 97,000 U.S. veterans, researchers found that those with any of several anxiety disorders had a higher risk of suffering a heart attack over the next seven years than vets without the mental health conditions.

The findings, reported in the American Heart Journal, build on evidence linking mental health to heart health.

A number of studies have found that people with clinical depression show a higher-than-average risk of heart disease. Less research, however, has focused on anxiety disorders. And because many people with clinical anxiety also suffer from depression, it has been unclear whether anxiety itself is strongly related to heart health.

In the new study, researchers found that several anxiety disorders - including post-traumatic stress disorder (PTSD), panic disorder and more generalized anxiety - were linked to heart attack risk independently of depression.

The findings show only an association between anxiety and heart attack, and do not prove cause-and-effect.

Moreover, there were only small absolute differences in heart attack rates between study participants with and without anxiety, according to the report.

Among veterans with generalized anxiety disorder, for example, 5.2 percent suffered a heart attack during the seven-year study period; that compared with 4.9 percent among vets without the disorder.

Similarly, heart attack rates among study participants with other anxiety disorders - including PTSD, panic disorder and obsessive-compulsive disorder - all hovered around 5 percent.

But when the researchers accounted for a number of other factors related to heart attack risk, people with anxiety disorders were anywhere from 25 percent to 43 percent more likely to suffer a heart attack than those with no anxiety disorders.

Those factors included age, smoking, drinking habits and conditions such as diabetes, high blood pressure and High cholesterol.

As for why clinical anxiety is related to heart attack, depression symptoms may play a role, according to the researchers, led by Dr. Jeffrey F. Scherrer of the St. Louis VA Medical Center.

They found, similar to past studies, that veterans with clinical depression had a higher heart attack risk than their non-depressed counterparts. And among veterans with depression, the association between anxiety disorders and heart attack risk was weaker.

That, Scherrer and his colleagues say, suggests that depression partly accounts for the link between anxiety disorders and heart attack.

Experts suspect that depression may affect heart disease risk through direct physiological effects. Research suggests, for example, that depression boosts the activity of platelets, cells that promote blood clotting. Depression may also have effects on the immune system or the sympathetic and parasympathetic nervous systems, which help regulate the heart’s response to everyday stresses.

Depression may also affect heart health in indirect ways. People with depression may, for instance, be less likely to exercise or eat well, or to stick with treatments for heart risk factors like high blood pressure.

Anxiety may affect the heart through at least some of those same pathways.

None of the veterans in this study had a known history of heart problems at the outset. Currently, the American Heart Association (AHA) does not recognize depression or anxiety as established risk factors for developing heart disease, Scherrer and his colleagues point out.

Since 2008, however, the AHA has recommended that people with existing heart disease be screened for depression, based on evidence tying depression to a poorer prognosis in heart patients.

Research has not yet shown whether treating depression and anxiety can lower the risk of developing heart disease, or improve the prognosis of people who already have it. More studies, Scherrer and his colleagues write, are needed to answer that question.

SOURCE:  American Heart Journal, May 2010.