The evidence on social isolation is clear. What to do about it is less so.

Loneliness is an especially tricky problem because accepting and declaring our loneliness carries profound stigma. Admitting we’re lonely can feel as if we’re admitting we’ve failed in life’s most fundamental domains: belonging, love, attachment. It attacks our basic instincts to save face, and makes it hard to ask for help.

I see this most acutely during the holidays when I care for hospitalized patients, some connected to I.V. poles in barren rooms devoid of family or friends — their aloneness amplified by cheerful Christmas movies playing on wall-mounted televisions. And hospitalized or not, many people report feeling lonelier, more depressed and less satisfied with life during the holiday season.

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.