"If I want to go into a high school and change physical activity or other obesity behaviors, I have to understand there are cliques and subgroups of students that exhibit different risks," said head researcher Thomas W. Valente.

Valente notes that previous recent research on social networks has shown that people can be influenced by their networks to adopt new behaviors, and he told Relaxnews that investigating Facebook and Twitter's roles in that is part of what he is investigating.

Valente and his team published an analysis on July 6 in the peer-reviewed journal Science that focuses on social networks and their influences. The goal of the project was to compile a collection of methods that public health advocates can use to stimulate changes in behaviour. While marketing and business areas have looked into Facebook and Twitter to research how social media influences behaviour, Valente says his research is the start of bringing the public health sector into the fold.

Some of his ideas include analysing social networks to spot which kids may be the most popular (and hence the most influential) and approaching them about promoting certain healthy behaviours among their peers; and scanning Facebook images to find kids who might be binge drinking or engaging in other risky behaviours and reaching out to not only those kids but others in their peer group, identified via tagged images.

"Existing evidence indicates that network interventions are quite effective," Valente writes. "Yet, the science of how networks can be used to accelerate behaviour change and improve organisational performance is still in its infancy."

According to a separate study published in Annals of Internal Medicine, the drinking habits of the people in your extended social group play a major role in determining your own rate of alcohol consumption.