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 subjectiveas 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.

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一项最新研究表明，保持快乐的心情是预防冬季生病的最佳良方。

研究人员让一群身体健康的志愿者接触感冒病毒或流感病毒，结果发现，性格开朗的人染病的几率较小。

这项研究结果在《身心医学》上发表。其主要依据是，"积极的情绪"有助于预防感冒和其它疾病。

研究人员认为，这可以从客观和主观两方面来解释，从客观上说，快乐的情绪可以增强人体的免疫力;从主观上说，快乐的人对于嗓子疼、流鼻涕等感冒症状没那么敏感。

研究报告的主要撰写人、匹兹堡卡内基·梅隆大学的谢尔登·科恩博士解释说：“‘情绪积极’的人对于病毒的免疫力较强。而且他们即使患了感冒，也觉得没什么大不了的。”

科恩博士和他的同事在此前的一项研究中发现，比较快乐的人不易患感冒，但不能完全确定这一性格本身是否具有这种“功效”。

在这项最新研究中，研究人员邀请了193名身体健康的成年人参加了性格特点、健康自评和情绪特点等各项标准测试，并将容易快乐、精力充沛、性格随和的人定义为“积极情绪者”，将经常不开心、精神紧张、不友好的人定义为“消极情绪者”。

研究人员将带有感冒病毒或某种流感病毒的滴鼻液滴进这些实验对象的鼻中。在接下来的六天里，实验对象要每天报告自己是否出现头痛、打喷嚏或鼻塞等症状，研究人员则收集实验对象的“日鼻涕量”等观察数据。根据所收集的数据，科恩和他的同事发现，性格开朗、比较快乐的人不容易患感冒。