Spread happiness, it's contagious.

By Eduardo Araia

What does the happiness of a friend of a friend of your friend have to do with you? If the first answer that comes to mind is "nothing," it's worth rethinking your concepts. That person – who may even be a complete stranger to you – does have a connection to you: if they are happy, your own chances of feeling happy increase by 6%.

The percentage emerged from the careful and, in many ways, surprising work that social scientist James Fowler of the University of California, San Diego, and Nicholas Christakis, a professor of sociology at Harvard Medical School, are doing on social relationships and their consequences on areas such as health and emotional states. In one of their most recent studies, they focused on happiness and showed that it spreads across various places through a social network. According to the researchers, it is not limited to passing from one person to another: it reaches individuals up to three degrees of separation. Furthermore, happiness seems to have a greater effect on a person's well-being than money – a considerable consolation in these times of still faltering economies in most of the world.

Fowler and Christakis' studies in this area are based on the Framingham Heart Study, an ambitious plan developed since 1948 by the National Heart Institute of the US government to deepen scientific knowledge about heart disease. From that year onward, thousands of residents of Framingham, Massachusetts, and their descendants began visiting a doctor every four years, on average, for a complete assessment of their personal health. The enormous amount of data collected can be used in various other areas of study, as Fowler and Christakis have demonstrated.

In the case of happiness, they used information from the Framingham survey to recreate a social network of 4.739 people whose happiness was measured between 1983 and 2003. In order to assess the participants' emotional well-being, they used responses to four items on the Center for Epidemiological Studies' Depression Scale: "I feel hopeful about the future"; "I am happy"; "I enjoy life"; and "I feel I am as good as other people."

One of the points highlighted by Fowler and Christakis is that happiness loves company. Happy people tend to group together, and initially, people with more social contacts seem happier. However, the study authors emphasize that the total number of social connections is not as important as the number of happy connections.

According to the research, happiness spreads through a social network up to three degrees of separation. Each person is 15% more likely to be happy if they are directly connected to a happy individual; 10% if they are friends with a friend who is happy; and 6% if they are friends with a friend of a happy friend. On average, each happy friend increases the chance of that person being touched by happiness by 9%.

Fowler and Christakis also observed the impact of unhappiness. According to them, every unhappy friend reduces the likelihood of a person feeling happy by 7%. Unhappiness also spreads, but less intensely.

The percentages may seem small, but Fowler draws attention to a detail in the Framingham study: an extra $5 in earnings represented, for the participants, an increase of only 2% in happiness. Another important aspect to consider, Fowler and Christakis point out, is the structure of connections: the position we occupy in the social network has a great impact on our level of happiness.

Researchers note that individual happiness depends not only on how many friends a person has, but also on how many friends their friends have. In social networking terms, this is called "centrality." The more central a person is—both in terms of the quality and quantity of their connections—the greater the chances that they will become happy. (But being happy doesn't necessarily mean expanding one's social circle, the researchers point out.)

The distance factor was also evaluated by Fowler and Christakis. According to their results, a happy friend who lives up to 1,6 kilometers from a person's home increases the likelihood of that person being happy by 25%. Friends who live further away do not show significant effects. Similar effects were recorded in siblings who live up to 1,6 kilometers from the home of the person studied and in spouses who live under the same roof, compared to siblings and spouses who live more than a mile away. Next-door neighbors also have a considerable influence: if they are happy, they increase the likelihood of the person feeling happy by 34%. More distant neighbors – even those living on the same block – do not have a significant impact.

Among the various practical implications of the work, Fowler highlighted one: the characteristic of happiness as a phenomenon intimately linked to the collective. According to him, it is up to us to assume greater responsibility for our happiness, as it affects dozens of other people. “The pursuit of happiness is not a solitary goal,” he stated. “We are connected, and so is our happiness.”