A study of the data from 5,000 individuals who par...  ...rchers to believe that loneliness spreads through social networks like a virus. The tendency to be a loner...  ...likely that they will attract or try to form new social ties," they write. Such friendless individuals en...  ...ss individuals ended up on t...

The Framingham Heart Study began in 1948 and follo...  ..., Massachusetts. In 2003, Nicholas Christakis, a social scientist and internist at Harvard, and James Fow...  ...track them down." Christakis and Fowler used the social data to study changes in the population over time...  ...time. They constructed netw...