To begin to tackle loneliness, it’s critical to understand it. Loneliness doesn’t necessarily mean that one is physically separated from others. It’s an all-consuming belief that one is socially isolated and cannot form meaningful connections with others.

It’s a shockingly common issue. Nearly three in five U.S. adults are considered lonely, according to data from Morning Consult. Underrepresented racial groups and people with low incomes are particularly likely to grapple with loneliness.

While loneliness lurks below the surface, it produces outsized health harms. Chronic loneliness rewires our brains and produces harmful inflammation. It fuels nearly every dangerous disease in the book, including high blood pressure, heart disease, obesity, depression, Alzheimer’s, cancer, and dementia. In fact, research has found that the health risks of prolonged loneliness are similar to those of smoking 15 cigarettes each and every day.

These health issues require patients to make frequent trips to the doctor–or worse, result in serious medical episodes. Those expenses add up fast and cost patients and our healthcare system dearly.

I know this all too well. My stepdaughter Rylie fatally lost her mental health battle in 2021 after living with chronic loneliness and bipolar for years. My wife and I were devastated. I was also deeply frustrated with the healthcare system for only treating her physical symptoms and missing the myriad of mental health warning signs.

You see, Rylie was no stranger to the ER. She often experienced episodes that required emergency care. Before her worst episodes, she expressed feeling an overwhelming sense of loneliness.

In total, she went to the hospital dozens of times over a period of two years, which cost hundreds of thousands of dollars.

The doctors always provided temporary solutions to her immediate issues. But the underlying loneliness–what was ultimately driving so many of her more severe episodes–went largely unaddressed.

Many families cannot afford such monstrous medical expenses–and would struggle to pay for other basic necessities like food and housing. I also shudder to think of the children who have lost their parents due to loneliness. Not only have they lost a crucial source of love and support, but also a vital financial caretaker. These children then grow up strapped for resources and face a higher risk of experiencing loneliness themselves. It’s a vicious cycle of poverty and mental health issues.

And then there’s the cost to our healthcare system. People experiencing loneliness use more inpatient care, go to the doctor more often, and are more likely to be hospitalized than those who don’t feel lonely–even though such excess care could be avoided. One analysis of four Dallas emergency rooms found that 80 people visited more than 5,000 times in a single year–largely because they were lonely. Those extra visits amount to longer waiting times and higher health costs for all patients.

Loneliness also takes a major toll on workers and employers at non-healthcare businesses. People experiencing loneliness simply can’t perform at their highest level. Lonely employees also face health issues more frequently, resulting in more missed days of work. And they’re more likely to seek employment elsewhere.

All told, loneliness could be costing the U.S. economy a whopping $406 billion annually.

We can’t afford to keep loneliness hidden in the background. The first step is screening. Generally, providers just assess physical symptoms–and perhaps delve into diet and exercise. But they also need to consider the mental health issues that could be at play, especially for people who end up in ER frequently.

Crucially, there should be a way for doctors to specifically diagnose people with loneliness and prescribe treatment, just like any other mental health condition.

Shedding the stigma around loneliness is equally critical. This has slowly happened with anxiety and depression, but not loneliness. People experiencing this condition already feel misunderstood and distrustful of others. Shaming or criticizing them for feeling that way worsens the issue and compels them to keep it hidden.

Loneliness is perhaps the biggest under-the-radar economic issue our country is facing. It’s costly–and deadly. It’s past time to address it.

Cindy Jordan is the co-founder and chief executive officer of Pyx Health, which supports individuals dealing with loneliness.

The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune.

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