Ask people what it takes to live a long life, and they'll say things like exercise, take Omega-3s, and see your doctor regularly.

Now research from Brigham Young University shows that loneliness and social isolation are just as much a threat to longevity as obesity.

"The effect of this is comparable to obesity, something that public health takes very seriously," said Julianne Holt-Lunstad, the lead study author. "We need to start taking our social relationships more seriously."

Loneliness and social isolation can look very different. For example, someone may be surrounded by many people but still feel alone. Other people may isolate themselves because they prefer to be alone. The effect on longevity, however, is much the same for those two scenarios.

The association between loneliness and risk for mortality among young populations is actually greater than among older populations. Although older people are more likely to be lonely and face a higher mortality risk, loneliness and social isolation better predict premature death among populations younger than 65 years.

"Not only are we at the highest recorded rate of living alone across the entire century, but we're at the highest recorded rates ever on the planet," said Tim Smith, co-author of the study. "With loneliness on the rise, we are predicting a possible loneliness epidemic in the future."

The study analyzed data from a variety of health studies. Altogether, the sample included more than 3 million participants from studies that included data for loneliness, social isolation, and living alone.

Controlling for variables such as socioeconomic status, age, gender, and pre-existing health conditions, they found that the effect goes both ways. The lack of social connections presents an added risk, and the existence of relationships provides a positive health effect. The new study appears in Perspectives on Psychological Science.

Previous research from Holt-Lunstad and Smith puts the heightened risk of mortality from loneliness in the same category as smoking 15 cigarettes a day and being an alcoholic. This current study suggests that not only is the risk for mortality in the same category as these well-known risk factors, it also surpasses health risks associated with obesity.

"In essence, the study is saying the more positive psychology we have in our world, the better we're able to function not just emotionally but physically," Smith said.

There are many things that help to subdue the effects of loneliness. With the evolution of the internet, people can keep in contact over distances that they couldn't before. However, the superficiality of some online experiences may miss emotional context and depth. Too much texting with each other can actually hurt a romantic relationship, for example. The authors of that texting study note, however, that saying something sweet or kind in a text is universally beneficial.

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