A talk with John Cacioppo

A Chicago scientist suggests that loneliness is a threat to your health

Americans are a lonely people, and given how we live, it's no wonder. We move often, we're more likely to live alone, we have lots of friends but few confidants, and we build our communities in ways that minimize unplanned interactions with others (aside from auto accidents).

All this loneliness isn't just making us unhappy. It may also be killing us. "Social isolation has an impact on health comparable to the effect of high blood pressure, lack of exercise, obesity, or smoking," according to "Loneliness: Human Nature and the Need for Social Connection," a new book by the University of Chicago psychologist John Cacioppo and the writer William Patrick.

Moving to a new town or being single can open the door to loneliness, but it turns out it isn't just a matter of being alone. Indeed, the lonely don't spend any more time by themselves than the rest of us do. Real loneliness is a feeling that some essential connection is lacking, and while social circumstances matter, it's also partly genetic.

Loneliness in our culture is embarrassing, perhaps in part because the lonely will settle for relationships that others might not. In a famous test called the Ultimatum Game, two people work as partners and one is given a sum of money to divide with the other. The recipient has sole discretion on dividing the loot, but the partner has the power to say no, whereby neither gets anything. Studies have shown again and again that the second partner will veto a split that seems unfairly low. Yet studies of lonely people show that they will settle for less than the non-lonely.

Loneliness also seems to impair people's self-control, including their ability to stick with a task. In one extraordinary test - in which subjects were asked to taste as many cookies as necessary to rate their flavor - those who were told no one wanted to work with them ate twice as many as those who were told everyone wanted to work with them. Being primed for loneliness also seemed to make the cookies taste better. (The lonely, by the way, eat a fattier diet even outside the lab, although they also substitute pets and computers for human connections.)

Cacioppo says he's about average when it comes to loneliness. At the very least, he avoided the isolation that comes of writing a book by taking on a coauthor.

IDEAS: What is the evidence that people are getting lonelier?

CACIOPPO: In 1984, the question was asked [in a survey], How many confidants do you have? And the most frequent answer was three. That question was repeated 20 years later, in 2004, and the most frequent response was zero.

IDEAS: Are you horrified by that?

CACIOPPO: I actually am. That's a stunning change, and it's a frightening change. People are not having fewer social contacts, but I think they are more harried social contacts - people now seek to have hundreds and thousands of "friends" on Facebook.

I think we've got it wrong. We have an apparatus [for social connection] that we inherited from 60,000 years ago that's largely unchanged, and we have made transitions in the last couple of thousand years like nothing we've seen in history. Just in the last 150 years have been dramatic, unbelievable social changes. Now, many of them have led to longer and healthier lives. But there are changes that we need not have perhaps taken, like being so isolated, that have led to some of the unhappiness and the health problems that we're seeing.

IDEAS: Is this a uniquely American problem?

CACIOPPO: Americans have more friends than Europeans on average. But what defines a friend is different in America than in Europe. In Europe, first of all, there's less mobility. There's a level of stability that we just don't know in America. But that same stability is connection, and those are threads of connection that I think lead to a definition of friends that is more high-quality.

IDEAS: To what extent is loneliness genetic and to what extent environmental or circumstantial?

CACIOPPO: Loneliness is about half heritable, half environmental. But what's being inherited seems to be the extent to which disconnection hurts. So it's not unlike the way salt sensitivity is inheritable. Some people if they eat salt, body water retention goes up, blood pressure goes up. I'm not sensitive, other people are. This is a signal that we all need to understand and attend to, just like hunger. It's a signal that's going wrong, and we tend to ignore it in our culture.

IDEAS: Why do we have such a signal?

CACIOPPO: It's evolutionary. It's because my ability to reproduce - to pass along my genes - depends on others around me. If I'm sitting there with a stick trying to fend off a tiger, I'm not going to last very long. I have to sleep. If I'm sleeping alone, I am especially vulnerable. So not too surprisingly from that evolutionary story, we predicted lonely individuals won't sleep less long, but their sleep will be less efficient, with more daytime fatigue. And we find that in longitudinal studies.

IDEAS: You say in the book that loneliness is dangerous. What are some of the ways?

CACIOPPO: It impairs physiological function - not being able to think as clearly, to self-regulate, and this can have serious consequences. We find lonely middle age and older adults are less likely to continue exercising. And once they stop, they don't start again. Loneliness also increases your level of depression.

IDEAS: Are the elderly especially lonely?

CACIOPPO: In old age we start to narrow the number of people we actually have contact with. We will have longer and more meaningful contact with fewer people. Sometimes we may reduce contact with family. You go to a few people with whom you have quality relationships, and I do mean a few, and what happens to these older people is, they get happier.

IDEAS: I took the loneliness quiz in your book and achieved a Unabomber-level score. What can people do to cut down on social isolation?

CACIOPPO: It's not the number of friends, it's the quality. Getting out of loneliness is within all our reach because it doesn't require being popular. Having a great friend can do wonders.

IDEAS: But if America is a lonely society, can't we get into a kind of social liquidity trap, in which each of us is wary and rejection-sensitive and seemingly unable to gain from interaction?

CACIOPPO: Just thank God it's only about 20 percent of the population that's feeling this way.

Daniel Akst is a writer in New York's Hudson Valley. John Cacioppo will be participating in a panel discussion at the Charles Hotel in Cambridge on Sept. 26 at 6 p.m. To reserve a seat, e-mail connection@harvard.com or call 617-661-1515.