Loneliness is part of the human condition. A primeval warning sign, like hunger or thirst, to seek out a primary resource: connection. Millions of years of evolution have shaped us into creatures who need social bonds in the same way that we need food and water.

And yet we increasingly find ourselves isolated. Loneliness is no longer a powerful enough driver to break us out of the silos created by modern life. Like our insatiable love of high-calorie foods, what was once an adaptive tool has become so misaligned with the way we live that it’s causing, in the words of the former surgeon general Vivek H Murthy, an “epidemic”.

It’s hard to compare our collective loneliness against that of previous generations, as we simply haven’t been measuring it consistently, but recent estimates suggest that anywhere from 22% to 75% of American adults are persistently lonely. A number of culture-wide structural changes might be to blame: more Americans live alone than ever before; fewer of us are marrying or having children; our average household size is shrinking. In many cases, these changes represent the availability of options where once the only accepted path was marriage and a nuclear family. But they also mean we are spending more time on our own. “Western societies have demoted human gregariousness from a necessity to an incidental,” writes John Cacioppo, a neuroscientist who studied social pain and passed away in March 2018, in his book Loneliness.

The trouble is that chronic loneliness doesn’t just make you feel terrible – it’s also terrible for you. Loneliness elevates our risk of developing a range of disorders, including cardiovascular disease, neurodegenerative diseases, cognitive decline, and metastatic cancer. It also weakens the immune system, making us more susceptible to infections. Left untended, even situational loneliness can ossify into a fixed state that changes brain structures and processes, says Stephanie Cacioppo, director of the Brain Dynamics Lab at the University of Chicago Pritzker School of Medicine. She is also John Cacioppo’s widow and was his research partner up until his death last year.

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