Emotional isolation is ranked as high a risk factor for mortality as smoking. A partial list of the physical diseases thought to be caused or exacerbated by loneliness would include Alzheimer’s, obesity, diabetes, high blood pressure, heart disease, neurodegenerative diseases, and even cancer—tumors can metastasize faster in lonely people.
Loneliness, she said—and this will surprise no one—is the want of intimacy…They insist that loneliness must be seen as an interior, subjective experience, not an external, objective condition. Loneliness “is not synonymous with being alone, nor does being with others guarantee protection from feelings of loneliness,” writes John Cacioppo, the leading psychologist on the subject. Cacioppo privileges the emotion over the social fact because—remarkably—he’s sure that it’s the feeling that wreaks havoc on the body and brain…Another school of thought insists that loneliness is a failure of social networks. The lonely get sicker than the non-lonely, because they don’t have people to take care of them; they don’t have social support.
A key part of feeling lonely is feeling rejected, and that, it turns out, is the most damaging part.
As expected, he found the students with bodily symptoms of distress (poor sleep, high cortisol) were not the ones with too few acquaintances, but the ones who were unhappy about not having made close friends. These students also had higher than normal vascular resistance, which is caused by the arteries narrowing as their tissue becomes inflamed. High vascular resistance contributes to high blood pressure; it makes the heart work harder to pump blood and wears out the blood vessels. If it goes on for a long time, it can morph into heart disease. While Cole discovered that loneliness could hasten death in sick people, Cacioppo showed that it could make well people sick—and through the same method: by putting the body in fight-or-flight mode.