Happiness is Contagious in Harvard Study
Happy Emotions Spread Through Three Degrees of Social Network
Dec 22, 2008
Happiness really is contagious, according to a new study released by Harvard Medical School. Happiness can spread through social networks like social contagion. One happy person can trigger a chain reaction that benefits friends, friends’ friends and friends’ friends’ friends.
The happiness effect that spreads through social networks can last for up to one year. Conversely, sadness does not spread through social networks as robustly as happiness.
Happiness Study
The study by Harvard Medical School and the University of California, San Diego is the first to demonstrate the indirect spread of happiness.
The study, described in a Harvard Medical School Press Release, looked at the happiness of nearly 5,000 people over a period of 20 years. Researchers found that when a person is happy the network effect can be measured up to three degrees. Therefore one person’s happiness can trigger a chain reaction that benefits their friends, their friends’ friends and their friends’ friends’ friends’. The happiness effect can last for up to a year.
Sadness does not spread through social networks as efficiently as happiness.
Emotional State Related to Social Network
“We’ve found that your emotional state may depend on the emotional experiences of people you don’t even know, who are two to three degrees removed from you,” says Harvard Medical School professor Nicholas Christakis, who, along with James Fowler from the University of California, San Diego co-authored this study. “And the effect isn’t just fleeting.”
Framingham Heart Study Data
Christakis and Fowler have been mining data from the Framingham Heart Study, a cardiovascular study that began in 1948. Researchers found a treasure trove of date dating back to 1971. Study participants in the Framingham Study had recorded all family changes, such as birth, marriage, death and divorce. In addition, participants had listed contact information for friends, coworkers and neighbors. Coincidently, many of the listed friends were also participants of the heart study. Researchers focused on 4,739 individuals and analyzed how happiness spread through over 50,000 social and family ties.
Using the Center for Epidemiological Studies Depression Index (a standard metric) that study participants completed, the researchers found that when an individual becomes happy, a friend living within a mile experiences a 25 percent increased chance of becoming happy. A co-resident spouse experiences an 8 percent increased chance, siblings living within one mile have a 14 percent increased chance, and for next door neighbors, 34 percent.
Surprise of Study: Indirect Effect of Happiness
The happiness effect on indirect relationships was the real surprise of the study. While an individual becoming happy increases a friend’s chances of happiness, a friend of that friend experiences a nearly 10 percent chance of increased happiness, and a friend of *that* friend has a 5.6 percent increased chance—a three-degree cascade of happy emotions.
“We’ve found that while all people are roughly six degrees separated from each other, our ability to influence others appears to stretch to only three degrees,” says Christakis. “It’s the difference between the structure and function of social networks.”
The Happiness study was published in the BMJ online publication for medical professionals on December 4, 2008.
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