Your personal happiness can be measured by your social network

Are your friends happy? What about their friends? These people, new research suggests, will have a profound impact on your own personal satisfaction.

Like an influenza outbreak, happiness – and misery too – spread through social networks, affecting people through three degrees of separation. For instance, a happy friend of a friend of a friend increases the chances of personal happiness by about 6% (see graphic, right).

Compare that to research showing that a $5000 income bump ups the odds by just 2%, says James Fowler, a political scientist at the University of California, San Diego, who led the new study.

“Even people we don’t know and have never met have bigger effect on our mood than substantial increases in income,” he says.


He and colleague Nicholas Christakis, of Boston’s Harvard Medical School, made the connection by mining 53,228 social connections between 5124 people who took part in a decades-long clinical study.

Emotional ripples

As part of the Framingham Heart Study, participants updated researchers on their social contacts and health status, including happiness, as measured by a standard psychological questionnaire. Many participants listed several other study participants, allowing the researchers to connect social dots.

Fowler and Christakis took a similar approach to document how obesity and cigarette smoking permeated through the same social network.

Even more than smoking and obesity, happiness spreads best at close distances, they found. A happy next-door neighbour ups the odds of person happiness by 34%, a sibling who lives within 1 mile (1.6 kilometres) by 14%, and a friend within half a mile by a whopping 42%.

The effect falls off through the network, with friends’ happiness boosting the chances of personal happiness by an average of 15% and friends of friends by 10%. As with obesity and smoking, Fowler and Christakis detected no effect beyond three degrees of separation.

While there might be six degrees of separation between any two people, “there are three degrees of influence,” Christakis says.

Fowler theorises that beyond three connections, a kind of social dissonance saps the transmission of behaviour, almost like a wave.

“If you drop one pebble in a pond, it will create ripples out from the pebble,” he says. “That’s not what’s happening here. You have a whole handful of pebbles and you’re throwing them in the pond at once.”

Contagious feeling

In the case of happiness, dour sentiments contain its infective spread. Fowler and Christakis found that each happy contact increases a person’s odds of happiness by an average of 9%, while an unhappy contact decreases those odds by 7%.

The long-time collaborators even bet over which emotion would spread more potently.

“I think that happiness is more likely to spread because here’s an emotion that’s about social cohesion,” says Fowler. Visible and contagious happiness might have helped our ancestors maintain social cohesion.

“In this rare occasion, James was right and I was wrong,” Christakis admits. “It’s pleasurable to be near other happy individuals and not near other unhappy individuals.”

Ruut Veenhoven, a sociologist at Erasmus University in Rotterdam, Netherlands, editor of the Journal of Happiness Studies, and curator of the World Database of Happiness agrees. “Happy people are typically more involved, are nicer to their kids and their dog, and live longer,” he says.

The study, which he describes as “terribly creative”, might even help people improve their daily lives. “If you want to make people happier, you know at least how it spreads.”

Journal reference: BMJ (DOI: 10.1136/bmj.a2338)