Recent studies have found that obesity, smoking and altruism can all spread through social networks, affecting not just our friends but their friends too. Now researchers from the University of California, San Diego and Harvard University have found that poor sleep and drug use can also spread through social networks. They studied 8,349 adolescents between year 7 and year 12 and found clusters of poor sleep and cannabis (marijuana) use that extended up to four degrees of separation within social networks. The researchers also found that it was the poor sleep that led on to cannabis use not vice versa.
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