Thanks to remarkable new technologies and the widespread use of social media, we are more “connected” than ever before. Yet as a nation, we are also more lonely. In fact, a recent study found that a staggering 47 percent of Americans often feel alone, left out and lacking meaningful connection with others. This is true for all ages, from teenagers to older adults.

The number of people who perceive themselves to be alone, isolated or distant from others has reached epidemic levels both in the United States and in other parts of the world. Indeed, almost two decades ago, the book Bowling Alone pointed to the increasing isolation of Americans and our consequent loss of “social capital.” In Japan, for example, an estimated half million (known as hikikomori) shut themselves away for months on end. In the United Kingdom, four in 10 citizens report feelings of chronic, profound loneliness, prompting the creation of a new cabinet-level position (the Minister for Loneliness) to combat the problem.

While this “epidemic” of loneliness is increasingly recognized as a social issue, what’s less well recognized is the role loneliness plays as a critical determinant of health. Loneliness can be deadly: this according to former Surgeon General Vivek Murthy, among others, who has stressed the significant health threat. Loneliness has been estimated to shorten a person’s life by 15 years, equivalent in impact to being obese or smoking 15 cigarettes per day. A recent study revealed a surprising association between loneliness and cancer mortality risk, pointing to the role loneliness plays in cancer’s course, including responsiveness to treatments.

Biologists have shown that feelings of loneliness trigger the release of stress hormones that in turn are associated with higher blood pressure, decreased resistance to infection and increased risk of cardiovascular disease and cancer. There’s even evidence that this perceived sense of social isolation accelerates cognitive and functional decline and can serve as a preclinical sign for Alzheimer’s disease.

It has long been recognized that social support—through the availability of nutritious food, safe housing and job opportunities—positively influences mental and physical health. Studies have repeatedly shown that those with fewer social connections have the highest mortality rates, highlighting that social isolation can threaten health through lack of access to clinical care, social services or needed support.

However, how the subjective sense of loneliness (experienced by many even while surrounded by others) is a threat to health, may be less intuitive. It is important to recognize that feelings of social cohesion, mutual trust and respect, within one’s community and among different sections of society, are all crucial to well-being. Perhaps this is especially so at a time of great social polarization exacerbated by contentious politics and vitriolic TV news.

These new statistics underscore the urgent need to address this “epidemic” of alienation and despair and to increase social support. For the first time in the U.S., life expectancy is declining, while the numbers of “deaths of despair” (from suicide, drugs and alcohol abuse), especially among white males, is on the rise. The chances of dying from an opioid overdose or suicide are now higher than the odds of dying in a motor vehicle accident.

So what can be done to combat widespread loneliness and anomie? The good news is there are models of success already in place in the U.S. and across the world. Programs such as Meals on Wheels and help-lines that arrange phone calls between volunteers and the lonely—whether they be older adults or teens in crisis—offer direct social support to those feeling profoundly isolated. Intergenerational initiatives, like the dementia-friendly villages in the Netherlands, the Intergenerational Learning Center in Seattle, and global home-sharing programs offer unique opportunities for the elderly to make meaningful connections with children and young adults.

Community engagement programs such as improvisational workshops at Chicago’s Second City aim to tackle social anxiety and feelings of isolation through laughter. And policy initiatives such as the Aspen Institute’s Weave: The Social Fabric project, New York’s Age-Friendly and England’s National Health Service provide strategic assistance—encouraging patients to engage in social activities rather than resorting to prescription drugs. And certainly information technology can be part of the solution as well: apps to “increase sociability” are being developed to combat loneliness. We have good models. We must prioritize further investment.

But perhaps, equally important, each of us can reach out to someone who may be lonely: the senior next door who never has visitors, the homeless person who feels invisible, or the mother overwhelmed with the responsibility of a new baby. By making a simple human connection, we can save a life.

Health and well-being are profoundly social. Ironically, in today’s hyperconnected world, we must tackle head-on the growing public health crisis of loneliness if we’re to become a healthier nation.