Happiness is 'infectious 'and spreads through friends and family

A study of the relationships of nearly 5,000 people tracked for decades in the Framingham Heart Study shows that good cheer spreads through social networks of nearby family, friends and neighbors.

In a study published online today by the British Medical Journal, scientists from Harvard University and UC San Diego showed that happiness spreads readily through social networks of family members, friends and neighbors.

Knowing someone who is happy makes you 15.3% more likely to be happy yourself, the study found. A happy friend of a friend increases your odds of happiness by 9.8%, and even your neighbor's sister's friend can give you a 5.6% boost.

The research is part of a growing trend to measure well-being as a crucial component of public health. Scientists have documented that people who describe themselves as happy are likely to live longer, even if they have a chronic illness.

Researchers studied complex social networks of more than 5,000 people and found that happiness is partly dependent on the mood of those near to you and their friends.

Professor Nicholas Christakis from Harvard Medical School and Professor James Fowler from the University of California, San Diego, found that a person’s proximity to happy people – specifically partners, siblings and neighbours – could make them happy too.

"Your emotional state depends not just on actions and choices that you make, but also on actions and choices of other people, many of which you don't even know," said Dr. Nicholas A. Christakis.

The researchers, writing in the British Medical Journal, found that clusters of happy and unhappy people were visible in the networks and the effect lasted for three degrees of separation - meaning one person benefitted from the happiness of their friends’ friends.

It suggests having frequent contact with other people is more important for the spread of happiness rather than the depth of the relationship, the authors said, because the closer people were physically the more likely the happiness was to be passed on.

If you have a friend who lives within a mile (about 1.6km) and who becomes happy it increases the probability that you will become happy by 25 per cent. Similar effects are seen in spouses who live together, siblings who live within a mile of each other and next door neighbours. But there is no effect on your own happiness if your co-workers are happy or not.

The authors said happiness genuinely spreads and the effect is not because happy people band together.

The same phenomenon has been seen in the spread of obesity and smoking, leading the authors to suggest it may also happen in other health-related behaviours such as depression, anxiety, loneliness, drinking, eating and exercise.

This means the spread of happiness through social networks could be used in public health policy as a positive emotional state has been shown to reduce illness and mortality, they said.

Professors Christakis and Fowler suggest the way happiness spreads like an infectious disease may be through mimicry and copying of facial expressions.

Other explanations include that happy people might share their good fortune, by being pragmatically helpful or financially generous to others, or change their behaviour towards others by being nicer or less hostile, or they merely exude an emotion that is genuinely contagious.

The study was based on data collected in the Framingham Heart Study, in which 5,124 adults aged 21-70 were recruited and followed between 1971 and 2003. (telegraph)