By Ben Schiller

Here's a new health risk to worry about as you get older: A lack of human contact. According to researchers from Brigham Young University, low social interaction has the equivalent lifespan impact as smoking 15 cigarettes daily, or being a raging alcoholic. Cutting yourself off from others is worse, even, than inactivity. And twice as bad as obesity. So, you better start making friends.

The research is based on a meta-analysis of 148 previously published studies measuring how often people interacted and their health outcomes.

The results, which appear in PLoS Medicine, are worrying because people are becoming more and more atomized. "The modern way of life in industrialized countries is greatly reducing the quantity and quality of social relationships," say the editors. "Many people in these countries no longer live in extended families or even near each other. Instead, they often live on the other side of the country or even across the world from their relatives."

And yet, "the idea that a lack of social relationships is a risk factor for death is still not widely recognized by health organizations and the public," the paper notes. It's an afterthought compared to smoking and drinking, despite evidence that the medical community could improve health by encouraging socialization. "People with stronger social relationships had a 50% increased likelihood of survival than those with weaker social relationships," the paper says.

The researchers speculate that stronger relationships with family and friends have a sort of positive feedback effect. Older people are better looked after, but they also take better care of themselves.

"Physicians, health professionals, educators, and the media should now acknowledge that social relationships influence the health outcomes of adults and should take social relationships as seriously as other risk factors that affect mortality," the editors say.

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