John Cacioppo, the director of the Center for Cognitive and Social Neuroscience at the University of Chicago, is the world's leading expert on loneliness. In his landmark book, Loneliness, released in 2008, he revealed just how profoundly the epidemic of loneliness is affecting the basic functions of human physiology. Cacioppo writes: "When we drew blood from our older adults and analyzed their white cells, we found that loneliness somehow penetrated the deepest recesses of the cell to alter the way genes were being expressed."

[In other words], when you are lonely, your whole body is lonely.