Happy is contagious

If you work in health care, you've probably heard of the famous Framingham Heart Study.  This particular study started way back in 1948 and followed a cohort of 5,209 adults living in Framingham, Massachusetts with the goal of identifying risk factors for cardiovascular disease.  Incredibly, when Congress commissioned the study, they selected the residents of Framingham over the residents of Paintsville, Kentucky, as the Framingham residents were more open to participating in research.  The study is now on its third generation and has produced over 3,000 peer-reviewed scientific publications.  

I recently came across one of these publications which appeared in the British Medical Journal, entitled "Dynamic spread of happiness in a large social network: Longitudinal analysis over 20 years in the Framingham Heart Study".  The study followed 5,124 individuals from the so-called "offspring cohort" (composed of most of the children of the original cohort, as well as their spouses) to evaluate whether happiness can spread from person to person.  In other words, the study investigators wanted to find out if happiness was contagious.

Happiness was measured using a previously validated questionairre.  The investigators used the emerging science of social networks to analyze both the number of connections that the study participants had with family members, friends, coworkers, and neighbors.  There were over 53,000 different social ties within the cohort, with an average of 10.4 ties to family, friends, and coworkers over the course of the study.  

The network map below shows that happy people tend to be connected to each other.  Each dot (called a node) represents an individual in the study (circles are females, squares are males).  The lines between nodes indicate the type of relationship between individuals (black for siblings, red for friends and spouses), while the color of the node indicates the degree of happiness (blue is least happy, yellow is most happy, and green is intermediate).

The clusters of happy and unhappy people are significantly larger than what would be expected based on pure chance.  Further analysis suggests that a person is 15% more likely to be happy if a direct connection is also happy - however, the impact of happiness goes out to three degrees of separation, with these individuals being 6% more likely to be happy.  Importantly, similar findings have been observed for more deleterious characteristics, such as obesity and smoking (i.e., people who are around others who smoke are more likely to smoke and people who are around others who are obese are more likely to be obese).  The investigators conclude that "People's happiness depends on the happiness of others to whom they are connected."

In my mind, these findings are incredibly important.  The more time we spend about people who are happy, the happier we will be!  Conversely, if we are happy, those around us will have a much greater likelihood of being happy too!  I've written about the power of happiness in the past (see "Don't worry, be happy!", "Happiness is the highest form of health", and "The mathematics of happiness").  What's really great about these findings from the Framingham Heart Study cohort is that happiness is contagious!