We know intuitively that loneliness and being alone are not the same thing. Solitude can be lovely. Crowded parties can be agony. We also know, thanks to a growing body of research on the topic, that loneliness is not a matter of external conditions; it is a psychological state. A 2005 analysis of data from a longitudinal study of Dutch twins showed that the tendency toward loneliness has roughly the same genetic component as other psychological problems such as neuroticism or anxiety.

Still, loneliness is slippery, a difficult state to define or diagnose. The best tool yet developed for measuring the condition is the UCLA Loneliness Scale, a series of 20 questions that all begin with this formulation: “How often do you feel …?” As in: “How often do you feel that you are ‘in tune’ with the people around you?” And: “How often do you feel that you lack companionship?” Measuring the condition in these terms, various studies have shown loneliness rising drastically over a very short period of recent history. A 2010 AARP survey found that 35 percent of adults older than 45 were chronically lonely, as opposed to 20 percent of a similar group only a decade earlier. According to a major study by a leading scholar of the subject, roughly 20 percent of Americans—about 60 million people—are unhappy with their lives because of loneliness. Across the Western world, physicians and nurses have begun to speak openly of an epidemic of loneliness.

The new studies on loneliness are beginning to yield some surprising preliminary findings about its mechanisms. Almost every factor that one might assume affects loneliness does so only some of the time, and only under certain circumstances. People who are married are less lonely than single people, one journal article suggests, but only if their spouses are confidants. If one’s spouse is not a confidant, marriage may not decrease loneliness. A belief in God might help, or it might not, as a 1990 German study comparing levels of religious feeling and levels of loneliness discovered. Active believers who saw God as abstract and helpful rather than as a wrathful, immediate presence were less lonely. “The mere belief in God,” the researchers concluded, “was relatively independent of loneliness.”

But it is clear that social interaction matters. Loneliness and being alone are not the same thing, but both are on the rise. We meet fewer people. We gather less. And when we gather, our bonds are less meaningful and less easy. The decrease in confidants—that is, in quality social connections—has been dramatic over the past 25 years. In one survey, the mean size of networks of personal confidants decreased from 2.94 people in 1985 to 2.08 in 2004. Similarly, in 1985, only 10 percent of Americans said they had no one with whom to discuss important matters, and 15 percent said they had only one such good friend. By 2004, 25 percent had nobody to talk to, and 20 percent had only one confidant.

In the face of this social disintegration, we have essentially hired an army of replacement confidants, an entire class of professional carers. As Ronald Dworkin pointed out in a 2010 paper for the Hoover Institution, in the late ’40s, the United States was home to 2,500 clinical psychologists, 30,000 social workers, and fewer than 500 marriage and family therapists. As of 2010, the country had 77,000 clinical psychologists, 192,000 clinical social workers, 400,000 nonclinical social workers, 50,000 marriage and family therapists, 105,000 mental-health counselors, 220,000 substance-abuse counselors, 17,000 nurse psychotherapists, and 30,000 life coaches. The majority of patients in therapy do not warrant a psychiatric diagnosis. This raft of psychic servants is helping us through what used to be called regular problems. We have outsourced the work of everyday caring.

We need professional carers more and more, because the threat of societal breakdown, once principally a matter of nostalgic lament, has morphed into an issue of public health. Being lonely is extremely bad for your health. If you’re lonely, you’re more likely to be put in a geriatric home at an earlier age than a similar person who isn’t lonely. You’re less likely to exercise. You’re more likely to be obese. You’re less likely to survive a serious operation and more likely to have hormonal imbalances. You are at greater risk of inflammation. Your memory may be worse. You are more likely to be depressed, to sleep badly, and to suffer dementia and general cognitive decline. Loneliness may not have killed Yvette Vickers, but it has been linked to a greater probability of having the kind of heart condition that did kill her.

And yet, despite its deleterious effect on health, loneliness is one of the first things ordinary Americans spend their money achieving. With money, you flee the cramped city to a house in the suburbs or, if you can afford it, a McMansion in the exurbs, inevitably spending more time in your car. Loneliness is at the American core, a by-product of a long-standing national appetite for independence: The Pilgrims who left Europe willingly abandoned the bonds and strictures of a society that could not accept their right to be different. They did not seek out loneliness, but they accepted it as the price of their autonomy. The cowboys who set off to explore a seemingly endless frontier likewise traded away personal ties in favor of pride and self-respect. The ultimate American icon is the astronaut: Who is more heroic, or more alone? The price of self-determination and self-reliance has often been loneliness. But Americans have always been willing to pay that price.

Today, the one common feature in American secular culture is its celebration of the self that breaks away from the constrictions of the family and the state, and, in its greatest expressions, from all limits entirely. The great American poem is Whitman’s “Song of Myself.” The great American essay is Emerson’s “Self-Reliance.” The great American novel is Melville’s Moby-Dick, the tale of a man on a quest so lonely that it is incomprehensible to those around him. American culture, high and low, is about self-expression and personal authenticity. Franklin Delano Roosevelt called individualism “the great watchword of American life.”