Happiness is infectious. It spreads through social networks, infecting people that you don’t even know. And it spreads more strongly than sadness does. That’s according to a recent study that examined the happiness of almost five thousand people over twenty years from 1983 to 2003.
The study was compiled by professors James Fowler of the University of California in San Diego and Nicholas Christakis of the Harvard Medical School. They examined records from a long-established heart study that included details of the emotional states of families and friends.
They found that, when you become happy, any friend of yours who lives within a mile becomes 25% more likely to also be happy. Amazingly, they also found that a friend of that friend becomes 10% more likely to happy, and a friend of that friend’s friend has a 5% increased chance of being happy.
They also found that people at the core of a local social network are more likely to be happy than people at the periphery. And they say that the reason seems to be that being at the core of the social network increases your happiness. It is not that being happy brings you to the core of the network.
Social networks spread happiness
The study followed the social networks of almost five thousand people over twenty years, including connections at one, two, three or more levels of separation. It found that happy people tend to be connected to each other. The clusters of happy and unhappy people are much larger than could be explainable by chance.
This takes into account several possible associations between happy people: your happiness might cause someone else to be happy; you might become connected because you are both already happy; or you might both be experiencing the same social conditions that might make you happy.
On average, you are 15% more likely to be happy if a person directly connected to you is happy. The chances increase or decrease depending on how close you are to the person. Mutual friends who live nearby have the strongest effect, and distant friends who live more than a mile away have little or no direct effect. Interestingly, neither do co-workers.
Happiness spreads more strongly through same-sex relationships. This means that your friends and neighbours might influence your happiness more than your spouse does. And your impact on a friend’s happiness gradually wears off over time, unless of course you keep in touch and stay happy.
However, there is an indirect effect that does not even depend on knowing the person. You are almost 10% more likely to be happy if a person two removes from you is happy (a friend of a friend). And you are over 5% more likely to be happy if a person three removes from you is happy (a friend of a friend of a friend).
Also, people at the core of a local social network are more likely to be happy than people at the periphery. And Christakis and Fowler say that the reason seems to be that being at the core of the social network increases your happiness. It is not that being happy brings you to the core of the network.
So, on average, having additional social contacts will help to make you happy – but only if your extra social contacts are happy themselves. Interestingly, happy people spread happiness much more strongly than unhappy people spread unhappiness.
However, the main effect on your happiness is your previous happiness: if you were happy the last time you were asked, you are three times more likely to be happy now than if you were unhappy the last time you were asked.
How the study was conducted
The Framingham Heart Study is an ongoing study, based in Massachusetts, that has examined 14,000 people spanning three generations of people, and their spouses. The three generations enrolled in 1948, 1971 and 2002.
Christakis and Fowler study focused on the middle group, because there is information available on their relationships with both their parents and their children, as well as with their friends.
On average, each person was connected to ten family members, friends or coworkers, and an indeterminate number of neighbours. Also, because the study took place in the same area, many of the connected people were also part of the study themselves.
The study measured people’s happiness by asking them how often they experienced four specific feelings during the previous week: “I felt hopeful about the future,” “I was happy,” “I enjoyed life,” “I felt that I was just as good as other people.”
Other studies have shown that these four questions are a reliable way of measuring happiness, and that the answers to each question are highly correlated to each other. As well as examining people’s happiness, this study also examined by how much their happiness changed over time.
Conclusions of the Study
Fowler and Christakis conclude that the spread of happiness seems to reach up to three degrees of separation, just like the spread of obesity and smoking behaviour. They believe that this finding has relevance for public health. Human happiness is not merely the province of isolated individuals.
They outline the following as already being known before their study:
- Previous work on happiness and wellbeing has focused on socioeconomic and genetic factors.
- Research on emotional contagion has shown that one person’s mood might fleetingly determine the mood of others.
- Whether happiness spreads broadly and more permanently across social networks is unknown.
They say that their study adds the following new information:
- Happiness is a network phenomenon, clustering in groups of people that extend up to three degrees of separation (for example, to one’s friends’ friends’ friends).
- Happiness spreads across a diverse array of social ties.
- Network characteristics independently predict which individuals will be happy years into the future.
- The illustration shows happiness clusters in over a thousand people in the Framingham social network during 1996 and 2000.
- Each node represents one person. Node colour indicates mean happiness of each person and all directly connected (distance 1) people: yellow is most happy, blue is least happy and green is in between.
- The full text of the study: Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study
- Homepage of James Fowler of the University of California in San Diego
- Homepage of Nicholas Christakis at Harvard Medical School
- Happiness Is A Collective Phenomenon
- The Happiness Virus