Greg Miller does an interesting review article in Science Magazine that describes numerous recent studies on the effect of loneliness on our physiology, health, and longevity. The article focuses on the work of John Cacioppo, a Univ. of Chicago psychologist who is credited with founding the field of social neuroscience. Here is the summary, followed by a few clips and rephrasings from the article:
In a steady stream of recent papers, social psychologists have identified several potentially unhealthy changes in the cardiovascular, immune, and nervous systems of chronically lonely people. The findings could help explain why epidemiological studies have often found that socially isolated people have shorter life spans and increased risk of a host of health problems, including infections, heart disease, and depression. The work also adds a new wrinkle, suggesting that it's the subjective experience of loneliness that's harmful, not the actual number of social contacts a person has. An impressive network of collaborations with researchers in other disciplines is now pioneering a new science of loneliness.
...scores of studies have found that people who lack social support are more prone to a variety of ailments. An analysis of 148 of these studies, published in the July 2010 issue of PLoS Medicine, suggests that social isolation increases the risk of death about as much as smoking cigarettes and more than either physical inactivity or obesity...loneliness is a health risk on its own, apart from conditions such as depression or stress that are common fellow travelers. More specifically, it seems to be the subjective experience of loneliness that's important for people's well-being rather than any objective measure of social connectivity (the number of close contacts someone has, for example).
The UCLA Loneliness Scale is based on a questionnaire that tries to size up how people perceive their social situation, with questions about how often they feel a lack of companionship, feel they have no one to talk to, or feel out of tune with those around them....When people score high on this scale, they also tend to exhibit several physiological changes that effectively put the body in a state of alert... people exhibit higher vascular resistance, a tightening of the arteries that raises blood pressure, forces the heart to work harder, and contributes to wear and tear on vessels...They have elevated molecular markers of stress - cortisol and epinephrine are elevated in saliva and urine, respectively.
Lonely people exhibit increased activity for several genes encoding signaling molecules that promote inflammation and decreased activity for genes that normally put the brakes on inflammation. They also show diminished activity in genes that help mount a defense against viral invaders....This..jibes with epidemiologic findings that socially isolated people are more susceptible to viruses, from the common cold to HIV, and to cardiovascular disease, which has been linked to excess inflammation.
Those who are lonelier, as rated by the UCLA Loneliness Scale, exhibit less activation in the ventral striatum, a component of the brain's reward circuitry, when they view pictures of smiling faces. They also show increased reactivity in the threat-detecting amygdala to pictures of angry or fearful faces.
...loneliness is partly heritable..a recent study, published in the July 2010 issue of Behavioral Genetics, used an abbreviated version of the UCLA Loneliness Scale in a survey sent to 8683 twins and family members. In this group, genetics accounted for 37% of the variability in loneliness, somewhat lower than in some previous studies. Overall, the heritability of loneliness is comparable to that of depression, but less than that of traits such as high blood pressure and cholesterol levels.
The news isn't all bad...Even for hard cases, Cacioppo believes loneliness can be overcome. He and colleagues recently conducted a meta-analysis of 20 studies on interventions for loneliness. Simply providing social support doesn't seem to work, especially if people know they're being looked after...The most effective interventions were those that borrowed methods from cognitive behavioral therapy to shift people's attention and interpretation of social situations in a more positive direction.