I read the quote below in this article, Alone in a Crowd by Robert Walter.
“I know of no more potent killer than isolation. There is no more destructive influence on physical and mental health than the isolation of you from me and us from them. It has been shown to be a central agent in the etiology of depression, paranoia, schizophrenia, rape, suicide, mass murder and a wide variety of disease states.”
Quoted in Strengthening Your Grip by Charles Swindoll