People who need people are not only the luckiest people in the world, but also the healthiest, according to a new study that measured how a person's sense of being part of a community affects physical and mental wellbeing.

The study found that physical health is closely related to how much "social capital" a person appears to have. Researchers defined social capital as the factors that add up to a feeling of connection to the community. Social capital was not found to affect rates of major depression.

"Social trust, sense of belonging and community participation were each significantly associated with health outcomes," according to the researchers.

The study used survey data on 944 pairs of twins who were part the National Survey of Midlife Development in the U.S.. By selectively studying twins, researchers were able to determine that the health benefits they found for social involvement were not the product of genetic factors.

"We directly compared twins, and found the effect of social trust regardless of genetics and upbringing," said study coauthor Takeo Fujiwara, chief of the Section of Behavioral Science, Department of Health Promotion and Research at the National Institute of Public Health in Japan.

Fujiwara and co-author Ichiro Kawachi, a professor of social epidemiology at the Harvard School of Public Health, say social capital includes factors such as community participation, volunteer work and comfort within a neighborhood.

"This is very encouraging," Fujiwara said. "What society or community can do may change the health of residents, regardless of predisposing factors."

The study appearing in the August issue of the American Journal of Preventive Medicine.