People whose levels of happiness and enthusiasm are higher than average also end up with less heart disease, according to a recent US study.

The researchers said that their study was the first of its kind in showing that happy emotions can be independently linked to a lower risk of coronary heart disease.

Lead researcher Karina Davidson of Columbia University Medical Center said that participants whose positive feelings were low had a 22% higher risk of heart attack or angina than did those who were even just slightly happier.

She said that risk was 22% lower for people whose levels of happiness were moderate, compared to people who experienced a little bit of happiness.

Heart disease is the number one cause of death in both Europe and the US.

For the study, Davidson's team followed about 1,700 Canadians who took part in a 10-year health survey.

When nurses made measurements of the subjects' apparent heart disease risk for the purposes of the survey, they also made note of the various emotional states the participants tended to feel.

They classified emotions such as depression and anixety under the broad umbrella of "negative affect" and those such as joy, happiness, and excitement under the term "positive affect".

The researchers asked people to rank themselves in terms of both negative and positive affect on a scale of one to five.

Davidson said that she thought enhancing people's happiness would be a good way to prevent heart disease.

She said that, while the people who experienced the most happiness had the lowest risk, some people belonging to this subgroup also experienced depression from time to time.

She said that occasional depression from otherwise happy people did not raise people's risk of heart disease.

Such diverse risk factors as income, intelligence, high blood pressure, smoking, being overweight, and having a family history of heart disease all contribute to heart risks.

Ellen Mason of the British Heart Foundation (BHF) said that she and her colleagues want to fund science that will unravel the biology that underlies the link between happiness and heart risk.

One thing that may link happiness with heart disease risk is that people who are happier tend to rest better and relax more, as well as needing less time to recover from stress.

The reasearchers said people should try to enjoy themselves.

Davidson said that people whose lifestyles encouraged them to take only two weeks' holiday never got around to doing the things they actually enjoyed.

She said that people should try to fit the things they enjoy into their schedules.

Ellen Mason of the British Heart Foundation suggested that the association between mood and health was not clear for her.

She said that she did not know if it was possible for people to change their natural levels of positivity.

Cardiologist Iain Simpson, of the British Cardiovascular Society, said that things like reducing cholesterol and diabetes were more important than happiness when it came to reducing heart disease.