New York had an “epidemic of loneliness.” Covid made it worse.

The result is a public health crisis on the scale of the opioid epidemic or obesity, said Dr. murthy. In a 2018 survey by the Kaiser Family Foundation, one in five Americans said they always or often felt lonely or socially isolated.

The pandemic has only exacerbated these feelings. In a recent citywide survey by the New York Health Department, 57 percent of people said they felt lonely sometimes or mostly, and two-thirds said they felt socially isolated in the past month.

“Loneliness,” said Dr. Murthy, “has real implications for our health and well-being.”

Being lonely, like other forms of stress, increases the risk of emotional disorders such as depression, anxiety and substance abuse. Less clear is that this also puts people at greater risk for physical conditions that appear to be unrelated, such as heart disease, cancer, stroke, high blood pressure, dementia and premature death. In lab experiments, lonely people exposed to a cold virus were more likely to develop symptoms than people who weren’t lonely.

An oft-cited meta-analysis by Julianne Holt-Lunstad of Brigham Young University compared the risk effects of loneliness, isolation and weak social networks to smoking 15 cigarettes a day.

“The general public recognizes how loneliness can affect our levels of distress, our emotional or mental health,” said Dr. Holt-Lunstad. “But we probably don’t recognize the robust evidence of its effects on our physical health.”

Nor do we recognize the economic costs.

According to studies by AARP and insurance giant Cigna, social isolation and loneliness are associated with an additional $6.7 billion in Medicare spending and cost employers more than $154 billion a year in stress-related absenteeism, plus increased job turnover.

Still, the culture has slowly evolved to deal with the epidemic, said Dr. Murthy, treating loneliness as an unpleasant feeling rather than a public health crisis. “There are more adults who struggle with loneliness than have diabetes,” he said. “But consider the discrepancy in the attention we give to these two conditions.”