Staying positive through the cold season could be your best defense against getting ill,a new American study suggests.

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

    Researchers believe the reasons may be both objective―as in happiness improving immune function―and subjective―as in happy people being less troubled by a sore 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 has found in a previous study that happier people seemed less likely to catch a cold, but some questions remained as to whether the emotional quality itself had the effect.

    For the new study,the researchers had 193 healthy adults complete standard measures of personality qualities, physicals 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.

    Afterwards,the researchers gave them nose drops containing either a cold virus or a particular flu virus.Over the next six days,the volunteers reported on any aches,pains,sneezing they had,while the researchers collected objective data.Cohen and his colleagues found that happy people were less likely to develop a cold.

    What's more,when happy folks did develop a cold,their symptoms were less severe than expected based on objective measures.

    On the contrary,people with negative characters were not at increased risk of developing a cold based on objective measures,though they did tend to get down about their symptoms.

    “We find that it's really positive emotions that have the big effect,” Cohen said,“not the negative ones.”

    So can a bad-tempered person fight a cold by deciding to be happy?