Loneliness, like happiness, can be contagious, according to a study published in the Journal of Personality and Social Psychology by John Cacioppo at the University of Chicago. His and other research shows that happiness can spread through social networks.

Cacioppo says that when a person feels lonely, they have more negative interactions than non-lonely people. He argues that a person in a negative mood is more likely to interact with someone else in a more negative way and that person is more likely to respond in a negative way.

Cacioppo also concluded that women are more likely than men to report "catching" loneliness and that the causes of becoming lonely were more likely to be changes in friendship networks rather than family.