They say heart attacks are not just the domain of hostile and explosive types, but nervous, withdrawn and chronically anxious people also have a higher risk.

The researchers at the University of Southern California in Los Angeles have found that men who scored the highest on tests of anxiety were 30 to 40 percent more likely than the others to have a heart attack, and these figures remained so even when the standard heart risks such as diet and smoking were taken into account.

Psychologist Biing-Jiun Shen and colleagues say that the results were over and beyond what might be explained by blood pressure, obesity, cholesterol, age, cigarette smoking, blood sugar levels and other cardiovascular risk factors.

Shen says older men with sustained and pervasive anxiety appear to be at increased risk for a heart attack even after their levels of depression, anger, hostility and type A behaviour are considered.

Type A personalities include people who are ambitious and assertive but it also often includes those who are hostile too.

Shen and colleagues analyzed data from the U.S. Normative Aging Study on 735 middle-aged or elderly men who underwent psychological tests in 1986.

At that time the men were in good health, and the researchers then followed up on them for a period of 12 years.

The researchers found that those who scored in the top 15 percentile for anxiety were more likely to suffer heart attacks later on and according to Shen that is not surprising.

Shen says the physiological reactions of anxiety are very similar to the signs and changes that are thought to lead to heart attacks and when a person is anxious the body reacts as if it is in danger and triggers a flight or fight response.

These reactions says Shen are very similar to those brought on by anger but fortunately nervous men can lower their risk of heart attack, as anxiety is very treatable.

The relationship between stress, psychological problems and coronary disease or other illnesses is a topic of close scientific scrutiny and many other researchers are attempting to unravel the link between anxiety and depression and other health problems.

Shen says more research is needed before it is know how much our brains influence our heart function and how much we can control what happens in the mind to prevent a heart attack.

The research is published in the Journal of the American College of Cardiology.