Over the last few years psychologists have become increasingly interested in the idea of social networks and there is evidence that these can influence people's happiness, smoking and exercise habits. Nicholas Christakis from Harvard University led a team of researchers looking into the effects of social networks on drinking. The team used data from the Framingham Heart Study which followed 12,067 people for more than 30 years. They found that people were 50% more likely to drink heavily if someone they were connected with also drank heavily and 36% more likely if a friend of a friend was a heavy drinker. The influence of heavy drinkers could be felt up to three degrees of separation away.
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