The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness

by Jonathan Haidt

Reason #3: Girls More Easily Share Emotions and Disorders We all know that our close friends can affect our moods. But did you know that your friends’ friends affect you too? The sociologist Nicholas Christakis and the political scientist James Fowler analyzed data from a long-running survey of the residents in Framingham, Massachusetts, called the Framingham Heart Study.[53] The study focused on physical health, but Christakis and Fowler were able to use items in the survey to study the way emotions moved through the community over time. They found that happiness tends to occur in clusters. This was not just because happy people seek each other out. Rather, when one person became happier, it increased the odds that their existing friends would become happier too. Amazingly, it also had an influence on their friends’ friends, and sometimes even on their friends’ friends’ friends. Happiness is contagious; it spreads through social networks.