An estimated 6 million adults in the U.S. suffer from panic disorder, with women twice as likely as men to develop the condition.

People with panic disorder experience sudden feelings of intense fear and loss of control, known as panic attacks, which also may be accompanied by physical symptoms like sweating, dizziness, racing heartbeat, and chest pain.

Past studies have suggested an association between panic attacks and cardiovascular events.

A 2007 study, for example, found older women who have at least one panic attack might be at higher risk of heart attack and stroke.

However, researchers said this link remained controversial, so they analyzed 12 studies involving one million men and women, 5,811 of whom had coronary artery disease.

Compared to people without panic disorder, those who did have the condition were found to have up to 36 percent higher risk of heart attack and up to 47 percent higher risk of heart disease.

The study did not prove a cause-and-effect relationship, but the findings suggest that people who experience panic attacks should closely monitor their heart health.

The research appeared in the journal Psychological Medicine.