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Social Networks and Public Health – The Hidden Influence of Social Networks

Social Networks and Public Health – The Hidden Influence of Social Networks

“We’re all embedded in massive social networks that have massive influences on our well-being,” claims Dr. Nicholas Christakis, a professor from Harvard University. In a recent TEDX talk, Dr. Christakis, argues that because people are inter-connected, their health must be interconnected as well.

In a study based off a population sample of 2,200 people from year 2000, Dr. Christakis first explores the relationship between network structure and obesity.


FIG 1: Social Network of 2,200 people. Yellow dots represent obesity. Red dots represent normal weight, from

According to Dr. Christakis’s study, obese people tend to be clustered with each other. This isn’t too surprising –people like to be friends with similar people or people who are close to them (as the strong triadic closure property suggests). More interestingly, however, Dr. Christakis provides evidence that obesity can be transmitted through a social network. If a randomly selected person in Dr. Christakis’s study has obese friends, it’s 45% more likely for that person to be obese as well. In a different study, in which he monitored a network of people for a five-year timeseries, he concluded that if your friend becomes obese during that five-year interval, it increases your risk of getting obese by at least 57%. Based on Dr. Christakis’s evidence, perhaps clustering of obesity occurs also due to exchange of beliefs / ideas regarding obesity between interconnected people.


FIG 2: Happiness Clusters in a Social Network. Yellow represents happy, green means neutral, and blue means sad.

Here, Dr. Christakis redemonstrates how social networks can potentially influence health, in a study regarding happiness. In this study, happiness (a very important health factor) also forms clusters in social networks. Dr. Christakis then argues that your position in the network can possibly affect your happiness. For example, if you are in a location where your connections are happy people, then you’re more likely to be happy. On the other hand, if your connections are sad, you are more likely to be sad.

In conclusion, Dr. Christakis demonstrates that whenever two humans are connected by an edge, that edge can potentially allow for each human to influence each other, either in a positive or negative way. Or, in other words, your life does not depend simply on your behavior, but also on the complex structure of the social network you are embedded in. The world today is highly interconnected, and understanding how network structure can affect human behavior can be highly useful in addressing societal problems, such as obesity or depression.


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