Ever wonder whether happy people have something you don't, something that keeps them cheerful, chipper and able to see the good in everything? It turns out they do — they have happy friends.

    That's the conclusion of researchers from Harvard and the University of California at San Diego, who report in the British Medical Journal online that happiness spreads among people like a salubrious disease. Dr. Nicholas Christakis and James Fowler studied nearly 5,000 people and their more than 50,000 social ties to family, friends and co-workers, and found that an individual's happiness is chiefly a collective affair, depending in large part on his or her friends' happiness — and the happiness of their friends' friends, and even the friends of their friends' friends.

     The merriment of one person, the researchers found, can ripple out and cause happiness in people up to three degrees away. So if you're happy, you increase the chance of joy in your close friend by 25%; a friend of that friend enjoys a 10% increased chance. And that friend's friend has a 5.6% higher chance.

    "This is a very serious piece of research. It's pioneering," says Dr. Richard Suzman, director of the division of behavioral and social research at the National Institute on Aging. "We are barely beginning to understand its translational and applied aspects."

    The authors analyzed data from the Framingham Heart Study, a historic study of heart disease among nearly 5,000 people begun in 1948. Because it was designed to follow participants and their offspring over several generations, the study's creators recorded detailed information about each person's closest relatives and friends, to better keep tabs on the original participants. That database served as an ideal social laboratory for Christakis and Fowler, who questioned each participant and his or her friends and family about their emotional state three times over 20 years.

    The idea of mood transfer is not exactly revolutionary. It makes sense, after all, that your happiness will affect your closest friends, and that their emotional state will influence your own. (Interestingly, the same association was not found with unhappiness, despite the old adage about misery and company, and the contagion effect was weaker among family members than friends, possibly because while people take a cue from friends, they take for granted their families and spouses.) What was less expected was that the effect was sustained up to three degrees of separation away, among people who may not necessarily know one another. You may owe your good cheer to your friend's brother's girlfriend, even if you don't know her name.

    That's the power of the social network, which, the authors argue, may impact our emotional state even more than our individual choices and environments. And it is not merely a result of like seeking like. The authors compared their observed network with a control network in which they randomly assigned feelings of happiness to individuals, and were able to rule out the possibility that happy people were simply clustering together by choice. Indeed, in another study in the same issue of the BMJ, researchers from Yale University and the Federal Reserve of Boston showed a similar tendency to cluster among people who, for example, are the same height, or suffer from acne, or headaches. But once the researchers adjusted for confounding factors, the network dissolved; in Christakis and Fowler's paper, the happiness link remained unbroken.

    But the effect was limited by space and time. Researchers found that the risk of catching happiness increased with proximity: so a next-door neighbor enjoys a 34% increased chance of happiness by living near a happy person, but a friend who lives across town is less affected. And the best-connected social networkers — those who were at the center of their social nodes — were more likely to become happy than people on the fringes. Viral happiness was relatively short lived, however, lasting about a year.

    This is the authors' third such networking study suggesting that the social group is a powerful super-organism that wields much influence over individuals' well-being. Previous analyses by Christakis and Fowler, based on the same pool of data, have shown that obesity is similarly contagious, as is the act of quitting smoking.

    The researchers' hope is that a better understanding of how people pick up and pass on behaviors will help health officials create more targeted public-health messages. Antismoking campaigns aimed at teens, for example, might be more powerful if they were geared toward the most socially connected students in a high school — rather than individual smokers. "We are always looking for areas to invest in, promising new areas of research that will give us new levels of ability to help people, and without a doubt I see this as a very promising area," says Suzman.

    總是在想那些快樂的人們是否擁有一些你所沒有的東西，可以讓他們保持快樂，爽朗，對于任何事物都能看到其好的一面？事實確實是那樣——他們擁有著快樂的朋友們。

    這是來自哈佛和圣地亞哥的加利福尼亞大學研究者的結論，他們在英國醫學雜志在線版上報告稱，快樂像一種有益健康的疾病，在人與人之間傳播開來。Nicholas Christakis 和 James Fowler博士研究了近5000人以及超過50000例他們與家人、朋友和同事間的社會關系，然后發現個人的快樂大多是一宗群體事件，大部分依賴于他們的朋友、朋友的朋友、甚至是朋友的朋友的朋友的快樂。研究者發現，一個人的快樂，會產生連鎖反應，給三方人群帶來快樂。因此，如果你快樂，你親密朋友快樂的機會會提高25%，他的朋友快樂的機會提高10%，而朋友的朋友的朋友快樂的機會提高5.6%。

     “這是一項非常重要的研究，具有開創性意義。”美國國家老年醫學研究中心行為與社會研究部門負責人Richard Suzman博士說，“我們才剛剛開始了解它的轉化和應用方面。”

    作者分析了來自弗雷明漢心臟研究的數據，這是一項關于心臟病方面的歷史性研究，開始于1948年，調查了近5000人。因為它旨在對參與者及其后的幾代后人進行跟蹤研究，該研究發起者詳細記錄下了參與者最親密的親屬及朋友的信息，以完善原始參與者的檔案。這個數據庫成了Christakis 和 Fowler 理想的社會實驗室，在20年間，他們對每個參與者及其家人朋友的情緒狀態進行了三次調查。

    關于情緒感染的說法并不是革命性的，它很容易說得通，畢竟你的快樂會影響你最親密的朋友，同樣，他們的情緒狀態也會影響你。（有趣的是，悲傷卻不存在這樣的關系，盡管有古話說同病相憐，但是悲傷情緒的傳播在朋友之間要比在家庭成員之間來的小，可能是因為需要從朋友那獲得安慰時，理所當然會先想到家人和配偶。）令人意外的是，這種效應會持續到第三方人群，他們不必認識彼此。就像你可能會從你的朋友的兄弟的女朋友那獲得快樂，即使你不知道她的名字。

    作者認為，這是由于社會網絡的力量，甚至會比我們的選擇和環境因素更多地影響我們的情緒狀態。這不是一個想當然的結論。作者設置了一個自然觀察組和一個對照控制組，在控制組中，他們把研究對象依據快樂情緒進行了隨機分配，從而排除了快樂人群因偶然性而聚集在一起的可能性。事實上，在另外一項由英國醫學雜志針對同一問題所作的研究中，來自于美國耶魯大學和波士頓美聯儲的研究人員，顯示了人們在聚集時有一個同樣的趨勢，比如說，擁有同樣的身高，或者同樣患有痤瘡，或者同樣有頭痛病。但是，當研究人員調整了研究的混雜因素時，這種網絡作用就消失了；而在Christakis 和 Fowler的論文中表明，快樂的聯結不會斷。

    但是這種影響受到空間和空間的限制。研究人員發現，獲取快樂的機會隨著距離的接近而增加。因此，住在一個快樂的人附近的鄰居獲得快樂的機會可以增加34%，而住在城市另一端的朋友受到的影響較小。那些聯系最緊密的社會關系人（處在他們社會關系網的中心的人們）會比那些處在社會關系網邊緣的人更容易獲得快樂。然而傳染的快樂持續的相對較短，大約一年時間。

    作者對于社會網絡的第三項研究表明，社會群體是一個強大的超級有機體，相比個人快樂，它發揮了更大影響力。基于相同的調查數據，Christakis 和 Fowler 此前的分析表明，肥胖同樣會傳染，如同戒煙行為一樣。

    研究人員們希望，通過對人們怎樣習得和傳遞行為建立一種更好的理解，可以幫助衛生官員采取更多有針對性的公共衛生措施。例如，針對青少年的反吸煙運動，針對處在緊密社會關系中的高中生會比針對個別吸煙者可能會更有效。“我們一直在尋找新的投資領域，希望新的研究領域能夠賦予我們新的能力去幫助他人，毫無疑問，我認為這是一個非常有前景的領域。”