First, incredibly, loneliness is contagious. A 2009 study using data collected from roughly 5,000 people and their offspring from Framingham, Massachusetts, since 1948 found that participants are 52 percent more likely to be lonely if someone they’re directly connected to (such as a friend, neighbor, co-worker, or family member) is lonely. People who aren’t lonely tend to then become lonelier if they’re around people who are.

Why? Lonely people are less able to pick up on positive social stimuli, like others’ attention and commitment signals, so they withdraw prematurely – in many cases before they’re actually socially isolated. Their inexplicable withdrawal may, in turn, make their close connections feel lonely too. Lonely people also tend to act “in a less trusting and more hostile fashion,” which may further sever social ties and impart loneliness to others.

This is how, as Dr. Nicholas Christakis told the New York Times in a 2009 article on the Framingham findings, one lonely person can “destabilize an entire social network,” like a single thread unraveling a sweater:

“If you’re lonely, you transmit loneliness, and then you cut the tie or the other person cuts the tie. But now that person has been affected, and they proceed to behave the same way. There is this cascade of loneliness that causes a disintegration of the social network.”