Loneliness is an invisible epidemic that affects 60 million Americans. Everyone feels lonely at times in their lives, but chronic loneliness poses a serious health risk. New research suggests that loneliness and social isolation are as much a threat to your health as obesity. As Richard Lang, MD, chair of preventive medicine at the Cleveland Clinic in Ohio puts it, people need to attend to loneliness in “the same way they would their diet, exercise, or how much sleep they get.”

According to University of Chicago social neuroscientist John Cacioppo, the effects of social isolation or rejection are as real as thirst, hunger, or pain. “For a social species, to be on the edge of the social perimeter is to be in a dangerous position,” says Cacioppo, who co-authored Loneliness: Human Nature and the Need for Social Connection. “The brain goes into a self-preservation state that brings with it a lot of unwanted effects.”

When your brain is on high alert, your body responds in kind. Morning levels of the stress hormone cortisol go up because you’re preparing for another stressful day. “We get a flatter diurnal cycle in that cortisol, which means it’s not shutting off as much at night,” Cacioppo says. As a result, sleep is more likely to be interrupted by micro-awakenings.

Cacioppo’s research suggests loneliness actually alters gene expressions, or “what genes are turned on and off in ways that help prepare the body for assaults, but that also increase the stress and aging on the body.” Animal studies have shown that social isolation alters levels of dopamine, a neurotransmitter that determines impulsive behavior.

The combination of toxic effects can impair cognitive performance, compromise the immune system, and increase the risk for vascular, inflammatory, and heart disease. Studies show that loneliness increases the risk for early death by 45 percent and the chance of developing dementia in later life by 64 percent. On the other hand, people who have strong ties to family and friends are as much as 50 percent less at risk of dying over any given period of time than those with fewer social connections.

A study presented at last month's Alzheimer's Association International Conference in Washington, D.C., found that loneliness is associated with accelerated cognitive decline in older adults. Researchers at Brigham and Women's Hospital and Harvard Medical School reported that the loneliest people in the study experienced cognitive decline at a rate approximately 20 percent faster over a 12-year period than people who were not lonely.

Research from Brigham Young University published earlier this year suggests that the health risk associated with loneliness or social isolation is “comparable to well-established risk factors” such as obesity, substance abuse, injury and violence, and environmental quality. “In light of mounting evidence that social isolation and loneliness are increasing in society, it seems prudent to add social isolation and loneliness to lists of public health concerns,” according to the study authors.

There’s nothing unusual about feeling lonely. “It’s perfectly common for people to experience loneliness when their social networks are changing, like going off to college or moving to a new city,” says Harry Reis, professor of psychology at the University of Rochester. The death of a loved one or marital discord can also trigger feelings of isolation. But there’s a difference between temporary “state” and chronic “trait” loneliness.

“Many of the patients we see have had situational loneliness that becomes chronic. They have been unable to rebuild after a loss or a move or retirement,” says psychiatrist Richard S. Schwartz, MD, co-author of The Lonely American: Drifting Apart in the Twenty-First Century. “One of the ways that situational loneliness can become chronic is precisely because of the shame we feel about our loneliness — the sense we have of being a loser.”

RELATED: Loneliness Is Bad For Your Health

“There’s a notion that lonely people are doing something wrong,” says author Emily White, who chronicled her own experience in Lonely: Learning to Live with Solitude. “Lack of social skills…lack of intelligence…less athletic. Notions we don’t bring to other similar psychological conditions like depression.”

Feeling lonely is not the same as being alone. “For some people, even though they have what on the outside looks like a social world, their internal experience is loneliness,” says Nadine Kaslow, PhD, professor of psychiatry and behavioral sciences at the Emory University School of Medicine, and chief psychologist of Grady Health System, both in Atlanta.

Reis believes loneliness is rooted in the quality of a person’s relationships. “It’s a lack of what we call intimate interaction…meaningful interactions where people are really connecting with the other person,” he says.

So what should a lonely person do?

First, recognize the loneliness. Loneliness is often equated with being a loser, “with holding up a big L over your head,” says Cacioppo. People tend to deny or conceal their loneliness, in which case it’s likely to get worse.

Second, understand what the loneliness is doing to your mind and body. “Unless you understand the psychological complexities of loneliness, you won’t understand what you’re doing,” says White.

Third, respond. “The idea is to reconnect safely,” says Cacioppo. Social media isn’t a substitute for face-to-face contact, but “it’s better than nothing.” White found her own feelings of loneliness began to change when she signed up for a women’s basketball league. “I was nervous. I was self-conscious. But I made myself do it,” she says.

A therapist can help, especially if loneliness is accompanied by feelings of anxiety or depression. “Loneliness promotes secrecy and distrust,” says White. “If you find someone outside of your social circle…you can talk really openly.”

If you know someone who’s lonely and you want to help, here are some of White’s suggestions:

Don’t text. Use the phone.

If you leave a message and don’t get a return call, call back.

Set up something low-key, like a walk. Keep the emotional temperature low.

Don’t diminish what the lonely person is going through.

Recognize that you may have to do more work to get the same level of response that you would get from another friend.

Simple acts of social interaction can make a big difference. So next time, just say “hello” — to the neighbor you brush past on the way to work, the sister you haven’t called in weeks, or the co-worker you rarely speak to by the coffee machine.

“If [a lonely person] is able make one more friend, the loneliness starts to diminish,” says Jacqueline Olds, MD, co-author of The Lonely American. “All sorts of scary things become possible when you have a friend to do them with.”