New research suggests that loneliness is not necessarily the result of poor social skills or lack of social support, but can be caused in part by unusual sensitivity to social cues. Lonely people are more likely to perceive ambiguous social cues negatively, and enter a self-preservation mind-set — worsening the problem. In this way, loneliness can be contagious: When one person becomes lonely, he withdraws from his social circle and causes others to do the same.

Dr. John Cacioppo, a psychology professor at the University of Chicago, has tested various approaches to treat loneliness. His work has found that the most effective interventions focus on addressing “maladaptive social cognition” — that is, helping people re-examine how they interact with others and perceive social cues. He is collaborating with the United States military to explore how social cognition training can help soldiers feel less isolated while deployed and after returning home.

The loneliness of older adults has different roots — often resulting from family members moving away and close friends passing away. As one senior put it, “Your world dies before you do.”

Ideally, experts say, neighborhoods and communities would keep an eye out for such older people and take steps to reduce social isolation. Ensuring they have easy access to transportation, through discounted bus passes or special transport services, can help maintain social connections.

Religious older people should be encouraged to continue regular attendance at services and may benefit from a sense of spirituality and community, as well as the watchful eye of fellow churchgoers. Those capable of caring for an animal might enjoy the companionship of a pet. And loved ones living far away from a parent or grandparent could ask a neighbor to check in periodically.

But more structured programs are arising, too. For example, Dr. Paul Tang of the Palo Alto Medical Foundation started a program called linkAges, a cross-generational service exchange inspired by the idea that everyone has something to offer.

The program works by allowing members to post online something they want help with: guitar lessons, a Scrabble partner, a ride to the doctor’s office. Others can then volunteer their time and skills to fill these needs and “bank” hours for when they need something themselves.

“In America, you almost need an excuse for knocking on a neighbor’s door,” Dr. Tang told me. “We want to break down those barriers.”

For example, a college student might see a post from an older man who needs help gardening. She helps him plant a row of flowers and “banks” two hours in the process. A few months later, when she wants to cook a Malaysian meal for her boyfriend, a retired chef comes by to give her cooking lessons.

“You don’t need a playmate every day,” Dr. Tang said. “But knowing you’re valued and a contributing member of society is incredibly reaffirming.”

The program now has hundreds of members in California and plans to expand to other areas of the country.

“We in the medical community have to ask ourselves: Are we controlling blood pressure or improving health and well-being?” Dr. Tang said. “I think you have to do the latter to do the former.”

A great paradox of our hyper-connected digital age is that we seem to be drifting apart. Increasingly, however, research confirms our deepest intuition: Human connection lies at the heart of human well-being. It’s up to all of us — doctors, patients, neighborhoods and communities — to maintain bonds where they’re fading, and create ones where they haven’t existed.