NEWSFOCUS

Why Loneliness Is Hazardous to Your Health

New research suggests that chronic loneliness can cause changes in the cardiovascular, immune, and nervous systems on January 18, 2011

EVERYONE KNOWS WHAT IT’S LIKE TO BE a lot more important than people thought it ity (29 July 1988, p. 540) prompted him to www.sciencemag.org lonely. It often happens during life’s tran- was,” Cacioppo says. change the focus of his research. Since then, sitions: when a student leaves home for Colleagues credit him with building an scores of studies have found that people who college, when an unmarried businessman impressive network of collaborations with lack social support are more prone to a vari- takes a job in a new city, or when an elderly researchers in other disciplines to pioneer ety of ailments. An analysis of 148 of these woman outlives her husband and friends. a new science of loneliness. “He’s placed it studies, published in the July 2010 issue of Bouts of loneliness are a melancholy fact of on the scientifi c map,” says one collaborator, PLoS Medicine, suggests that social isola-

human existence. Dorret Boomsma, a behavioral geneticist at tion increases the risk of death about as much Downloaded from But when loneliness becomes a chronic Vrije Universiteit Amsterdam in the Nether- as smoking cigarettes and more than either condition, the impact can be far more seri- lands. “He’s doing very creative work,” says physical inactivity or obesity. ous, says John Cacioppo, a social psycholo- Martha Farah, a cognitive neuroscientist at the Compelling as these epidemiological gist at the University of Chicago in Illinois. University of Pennsylvania. “He’s created a studies are, Cacioppo says, they leave unan- Cacioppo studies the biological effects of new way of thinking about the biol- swered many questions about the loneliness, and in a steady stream of recent ogy of interpersonal relationships.” Online mechanisms involved and about papers, he and collaborators have identifi ed what aspects of social isola- several potentially unhealthy changes in the A new beginning sciencemag.org tion are responsible. In the early cardiovascular, immune, and nervous sys- Cacioppo hasn’t always studied Podcast interview 1990s, he set out to tackle these with author tems of chronically lonely people. Their fi nd- loneliness. In the 1980s and ’90s, Greg Miller. questions. He began by hand- ings could help explain why epidemiological he made a name for himself with ing out questionnaires to thou- studies have often found that socially isolated meticulous laboratory studies on various sands of students at Ohio State University in people have shorter life spans and increased aspects of emotion and cognition, and he’s Columbus, where he was based at the time, risk of a host of health problems, including a founder of the fi eld of social neuroscience, and following up with physiological and infections, heart disease, and depression. which seeks to understand the brain’s role psychological testing in the lab. For the past Their work also adds a new wrinkle, suggest- in social behavior. (Last month, colleagues 10 years, he has been testing hundreds of ing that it’s the subjective experience of lone- elected him president of the newly formed Chicago-area residents, working closely liness that’s harmful, not the actual number Society for Social Neuroscience.) with psychologist Louise Hawkley and other of social contacts a person has. “Loneliness Cacioppo says a 1988 Science paper sug- University of Chicago colleagues.

isn’t at all what people thought it was, and it’s gesting that social isolation increases mortal- This work has convinced Cacioppo that HOPPER/THE EDWARD LIBRARY BRIDGEMAN ART CREDIT:

138 14 JANUARY 2011 VOL 331 SCIENCE www.sciencemag.org Published by AAAS NEWSFOCUS

loneliness is a health risk on its own, apart “Those were landmark investigations” other colleagues to investigate gene activity from conditions such as depression or stress that got other researchers interested in poten- across the genome in the white blood cells that are common fellow travelers. More tial biological effects of loneliness, says of 14 participants in a longitudinal study of specifically, it seems to be the subjective Chris Segrin, a behavioral scientist at the loneliness among Chicago-area residents. experience of loneliness that’s important for University of Arizona in Tucson. The volunteers selected scored in either the people’s well-being rather than any objective Lonely people also have elevated molec- top or the bottom 15% of the study cohort on measure of social connectivity (the number ular markers of stress. Cacioppo’s group has the UCLA Loneliness Scale. of close contacts someone has, for exam- found that cortisol and epinephrine are ele- Two differences between the groups ple). It’s an important distinction that most vated in saliva and urine, respectively. That stood out: Lonely people exhibited increased previous studies had ignored, says Daniel might help explain why lonely people report activity for several genes encoding signaling Russell, a psychologist at Iowa State Univer- feeling more stressed in situations most peo- molecules that promote infl ammation and sity in Ames. “Some people are socially iso- ple experience as only moderately stressful, decreased activity for genes that normally lated and they’re not lonely,” Russell says. such as public speaking, Cacioppo says. put the brakes on infl ammation. They also “By contrast, some people are lonely even if Together, these findings point to acti- showed diminished activity in genes that they have a lot of social contacts.” vation of the sympathetic nervous system, help mount a defense against viral invaders. As a graduate student in the 1970s at which coordinates the body’s fi ght-or-fl ight Cole says that jibes with epidemiologic the University of California, Los Angeles responses. It’s as if loneliness prepares the findings that socially isolated people are (UCLA), Russell helped develop the scale body for some looming threat. Cacioppo more susceptible to viruses, from the com- Cacioppo now uses in most of his research. thinks that makes evolutionary sense. He mon cold to HIV, and to cardiovascular The UCLA Loneliness Scale is based on a argues that being alone, for our distant disease, which has been linked to excess questionnaire that tries to size up how people ancestors, meant abandoning the protection infl ammation. Cole says the team will soon on January 18, 2011 (DECEMBER 2009) AMERICAN PSYCHOLOGICAL ASSOCIATION PSYCHOLOGICAL 2009) AMERICAN 97 (DECEMBER www.sciencemag.org

“Loneliness … [is] a lot

JOURNAL PERSONALITY OF AND SOCIAL PSYCHOLOGY , more important than people Downloaded from thought it was.” Clusters of loneliness. Loneliness tends to spread among people on the fringes of social networks, —JOHN CACIOPPO, according to a 2009 study. Blue dots represent people who reported feeling lonely three or more days UNIVERSITY OF CHICAGO a week, green corresponds to two lonely days, and yellow corresponds to less than two lonely days.

perceive their social situation, with questions of the group and jeopardizing one’s genetic publish a replication of the findings in a about how often they feel a lack of compan- contribution to the next generation. He pos- group of about 120 participants in the Chi- ionship, feel they have no one to talk to, or its that the physiological changes and anxi- cago study. He notes that just feeling a lit- feel out of tune with those around them. ety that accompany loneliness are a warn- tle left out isn’t likely to throw the immune ing that an individual’s social ties have got- system out of whack. “It really takes a per- Sympathetic feelings ten too weak: “It’s an aversive signal that son who has taken and consolidated a lonely When people score high on the UCLA motivates us to change our behavior in a way view of the world to show these changes in Loneliness Scale, Cacioppo and colleagues that’s good for our genetic survival.” In his gene expression,” he says. have found, they also tend to exhibit sev- view, loneliness is a double-edged sword— Loneliness not only increases wear and eral physiological changes that effectively adaptive in the short term but dangerous tear by keeping the body in alert mode but put the body in a state of alert. In one early when it becomes chronic. also may prevent people from recharging study, they found that lonely people exhibit Cacioppo and colleagues have also found their batteries with rest and relaxation. In higher vascular resistance, a tightening of evidence that loneliness has a direct impact the March 2010 issue of Health Psychol- the arteries that raises blood pressure. That on the immune system. In a 2007 study in ogy, Cacioppo and colleagues reported forces the heart to work harder and can con- Genome Biology, Cacioppo teamed up with that although lonely people sleep a normal

CREDITS (LEFT TO RIGHT): DAN DRY/COURTESY UNIVERSITYCHICAGO;ET AL. OF J. CACIOPPO , CREDITSRIGHT):(LEFT TO DAN DRY/COURTESY tribute to wear and tear on vessels. UCLA genomics researcher Steve Cole and number of hours, they report more fatigue

www.sciencemag.org SCIENCE VOL 331 14 JANUARY 2011 139 Published by AAAS NEWSFOCUS

the next day, suggesting that their qual- social support. (They did not measure lone- by Russell have shown. College freshmen ity of sleep isn’t as good. Segrin says his liness per se.) To Hariri, the fi ndings, pub- rank among the loneliest populations he and group has recently replicated this fi nding lished online 31 August in Neuropsycho- his colleagues have studied, because they’ve and extended it to show that lonely people logia, suggest that people’s perceptions of left behind their family and high school derive less satisfaction from leisure activ- social support may calibrate how the amyg- friends and are trying to fi nd their way in a ities. Their fi ndings are in press at Health dala assesses social threats, which in turn new social ecosystem, Russell says. Communications. could infl uence their risk for anxiety disor- According to some measures, society ders or other conditions. is changing in ways that may make peo- The lonely brain Loneliness may also affect the prefrontal ple even lonelier. The U.S. Census Bureau Studies by Cacioppo and others before him cortex, a region important for what cognitive estimates that nearly 29 million people live have found that lonely people tend to rate scientists call executive control. In daily life, alone in the United States, a 30% increase their own social interactions more negatively that often translates to restraint—as in not from 1980. A widely cited 2006 study in and form worse impres- eating cheeseburgers at American Sociological Review asked a rep- sions of people they meet. every meal or putting the resentative sample of the U.S. population Researchers are begin- stopper back in the wine how many people they would feel comfort- ning to show how these bottle after one or two able discussing an important personal issue biases may be encoded in glasses. Epidemiological with. Between 1985 and 2004, the average the brain. In a 2008 study studies have suggested number dropped from three to two, and the in the Journal of Cognitive that people with poor percentage of people who reported having Neuroscience, Cacioppo social networks are more no such confi dants rose from 10% to 25%. and colleagues used func- likely to eat poorly, con- And like certain other health risks, loneli- tional magnetic reso- sume more alcohol, and ness may be contagious. Cacioppo recently nance imaging to measure exercise less. Several stud- teamed up with James Fowler of UC San metabolic activity in the ies have found that lonely Diego and Nicholas Christakis of Harvard

brains of 23 undergraduate Unrewarding. Lonely people take less people perform poorly on University to investigate the spread of lone- on January 18, 2011 women at the University enjoyment from social interactions lab tests that require exec- liness through social networks. Scrutiniz- of Chicago. Those who and exhibit less activity (blue) in the utive control, and at least ing data on thousands of people participat- were lonelier, as rated by ventral striatum. one study, published in the ing in the Framingham Heart Study, Fowler the UCLA Loneliness June 2006 issue of Social and Christakis have reported that everything Scale, exhibited less activation in the ventral Neuroscience, found reduced prefrontal cor- from smoking habits to happiness appears to striatum, a component of the brain’s reward tex activity in socially isolated people. spread from person to person within social circuitry, when they viewed pictures of smil- networks (Science, 23 January 2009, p. 454). ing faces. Contagious … but curable So, too, can loneliness, the trio reported in In another study, Cacioppo and colleagues Evidence that loneliness is partly heritable December 2009 in the Journal of Personality www.sciencemag.org asked lonely and nonlonely people to per- has emerged from a collaboration between and Social Psychology. form the Stroop test, a workhorse task in Cacioppo and Boomsma, who oversees The news isn’t all bad, however. Even for experimental psychology in which people see a database of Dutch twins and their fam- hard cases, Cacioppo believes loneliness can words presented in colored text one by one on ily members. They’ve found that genetics be overcome. He and colleagues recently a computer screen, then indicate what color accounts for up to half of the individual vari- conducted a meta-analysis of 20 studies on it was. When lonely people saw words that ation in loneliness. Their most recent study, interventions for loneliness. Simply provid-

evoked negative social interactions, such as published in the July 2010 issue of Behav- ing social support doesn’t seem to work, Downloaded from “isolate” or “reject,” they took a split second ioral Genetics, used an abbreviated version especially if people know they’re being longer to identify the color than they did for of the UCLA Loneliness Scale in a survey looked after. “If you know people are stop- negative nonsocial words, such as “vomit.” sent to 8683 twins and family members. In ping by to check on you, it makes you feel Nonlonely people showed no such delay. To this group, genetics accounted for 37% of like more of a loser,” Cacioppo says. The (JANUARY 2009) 21 (JANUARY Cacioppo, the fi ndings, as yet unpublished, the variability in loneliness, somewhat lower most effective interventions were those that suggest that lonely people pay extra attention than in some previous studies. Overall, the borrowed methods from cognitive behav- to negative social cues. “It suggests the brain heritability of loneliness is comparable to ioral therapy to shift people’s attention and is on the alert for social threats,” he says. that of depression, Boomsma says, but less interpretation of social situations in a more A recent study by researchers at Duke than that of traits such as high blood pressure positive direction, the team reported online University in Durham, North Carolina, and cholesterol levels. 17 August 2010 in Personality and Social meshes with these fi ndings. Neuroscientist In his 2008 book, Loneliness: Human Psychology Review. Ahmad Hariri and colleagues set out to rep- Nature and the Need for Social Connec- As for preventing loneliness, Cacioppo licate previous reports that people with anx- tion, Cacioppo hypothesizes that there is a says it helps to know where your own ther- ious tendencies (but not a clinical diagno- “genetic thermostat” for loneliness that’s set mostat is set and strive to stay in your com- COGNITIVENEUROSCIENCE JOURNAL OF , sis) exhibit more activity in the amygdala, differently in different people. That setting fort zone. In Loneliness, he writes: “The a brain region crucial for threat detection, determines the degree of distress triggered degree of social connection that can improve when they see images of angry or fearful by social isolation. “You’re not inheriting our health and our happiness … is both as faces. But Hariri’s group found that this was loneliness; you’re inheriting how painful it simple and as diffi cult as being open and true only for the subset of the volunteers feels to be alone,” Cacioppo says. available to others.”

who also reported below-average levels of But environment matters, too, as studies –GREG MILLER ET AL. , CACIOPPO J. CREDIT:

140 14 JANUARY 2011 VOL 331 SCIENCE www.sciencemag.org Published by AAAS