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Happiness is infectious

Happiness really does rub off – a person's happiness depends on the happiness of others with whom they are connected, finds research published on today.

Happiness is not just an individual experience or choice, but is dependent on the happiness of others to whom individuals are connected directly and indirectly, and requires close proximity to spread, say the authors. For example, a friend who becomes happy and lives within a mile increases your likelihood of happiness by 25%.

Professor Nicholas Christakis from Harvard Medical School and Professor James Fowler from the University of California, San Diego, analysed data collected in the  Framingham Heart Study to find out if happiness can spread from person to person and if clusters of happiness form within social networks. 

Using statistical analysis the researchers measured how social networks were correlated with reported happiness. They found that live-in partners who become happy increase the likelihood of their partner being happy by 8%, similar effects were seen for siblings who live close by (14%) and neighbours (34%). Work colleagues did not affect happiness levels suggesting that social context may curtail the spread of emotional states.

Interestingly, it is not only immediate social ties that have an impact on happiness levels, the relationship between people's happiness can extend up to three degrees of separation (to the friend of one's friends' friend). Indeed, people who are surrounded by happy people are likely to become happy in the future.

The findings suggest that clusters of happiness result from the spread of happiness and not just a tendency for people to associate with similar individuals.

The authors say: "Changes in individual happiness can ripple through social networks and generate large scale structure in the network, giving rise to clusters of happy and unhappy individuals."