It’s been well established that social isolation is a serious health risk, particularly for seniors. A 2010 study showed that too much alone time can be just as dangerous as smoking 15 cigarettes a day. Many scientists have assumed that loneliness is the culprit, and subsequent research has backed this suspicion. But a new study is overturning this view, showing that even people who don’t mind being alone are still significantly more likely to die when their social networks are diminished.

The results suggest that lack of social contact is a more significant risk factor than loneliness.

“In many ways, social isolation and loneliness are two sides of the same coin,”explained Steptoe. “Social isolation indicates a lack of contact with friends, relatives and organizations, while loneliness is a subjective experience of lack of companionship and social contact.”

But why isolation is such a potent predictor of death isn’t immediately obvious.

According to Julianne Holt-Lunstad, there may be two possible mechanisms by which a thriving social network of friends and family could contribute to good health.

First, the ongoing support of other people may reduce the harmful effects of stress (even if someone is happy in their solitude); it could be that isolation reduces immune function. And second, the influence of others may also encourage behaviour that contributes to good health (such as eating properly, taking medications, and practicing proper hygiene).

Steptoe agrees, saying that, “When you’re socially isolated, you not only lack companionship in many cases, but you may also lack advice and support from people.”

It’s worth noting that the Steptoe study looked at people over the age of 50. But other research has shown that social isolation is a risk factor for all people, regardless of age.