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Positive friends can lead to a longer life (Robert Alison, 8/02/2010, Winnipeg Free Press)

Research by Bruce Sacerdote at Dartmouth College, and others, shows that clusters of friends "infect" each other with obesity and unhappiness. Friends comprising social groups often become obese simultaneously, and according to researchers, an individual is 57 per cent more apt to become obese if friends are obese.

According to information presented at the 2009 Midwest Political Science Association Annual Conference, social networking influences candidate evaluations in elections.

Extensive research by Lisa Berkman at the Harvard School of Public Health, found that "the degree to which an individual is interconnected and embedded" in a social network is vital to one's health.

"Social integration and cohesion influence mortality," she says. "Social facts explain disease patterns, especially serious diseases.

"Studies consistently show that the lack of social ties or social networks predict mortality for almost every cause of death," she concluded.

Longer lifespans and good health often depend on "close friends and relatives, marital status and affiliations or memberships in religious and volunteering associations," the researchers say.

The degree of one's social integration is the "underlying explanation for suicide rates, they added.