Staying positive could be the best defense against getting ill in winter,a new study suggests.

Staying positive through the cold season could be your best defense against getting ill, new study findings suggest.

In an experiment that exposed healthy volunteers to a cold or flu virus, researchers found that people with a generally sunny disposition were less likely to fall ill.

The findings, published in the journal Psychosomatic Medicine, build on evidence that a "positive emotional style" can help ward off the common cold and other illnesses.

Researchers believe the reasons may be both objective as in happiness boosting immune function and subjective as in happy people being less troubled by a scratchy throat or runny nose.

"People with a positive emotional style may have different immune responses to the virus," explained lead study author Dr Sheldon Cohen of Carnegie Mellon University in Pittsburgh. "And when they do get a cold, they may interpret their illness as being less severe."

Cohen and his colleagues had found in a previous study that happier people seemed less susceptible to catching a cold, but some questions remained as to whether the emotional trait itself had the effect.

For the new study, the researchers had 193 healthy adults complete standard measures of personality traits, self-perceived health and emotional "style." Those who tended to be happy, energetic and easy-going were judged as having a positive emotional style, while those who were often unhappy, tense and hostile had a negative style.

The researchers gave them nasal drops containing either a cold virus or a particular flu virus. Over the next six days, the volunteers reported on any aches, pains, sneezing or congestion they had, while the researchers collected objective data, like daily mucus production. Cohen and his colleagues found that based on objective measures of nasal woes, happy people were less likely to develop a cold.