Being CEO has its many perks: Business leaders get to command the world's most powerful companies, shape their legacies as pioneers of industry, and enjoy hefty billion-dollar paychecks. But in the steep climb up the corporate ladder, many won't notice all the peers left behind until they're looking down from the very top. It can be a lonely, solitary job.

Leaders at some of the world's largest companies---from Airbnb and UPS to PepsiCo and Apple---are finally opening up about the mental toll that comes with the job. As it turns out, many industry trailblazers are grappling with intense loneliness; at least 40% of executives are thinking of leaving their job, mainly because they're lacking energy and feel alone in handling daily challenges, according to a Harvard Medical School professor. And the number could even be higher: About 70% of C-suite leaders “are seriously considering quitting for a job that better supports their well-being,” according to a 2022 Deloitte study.

To ward off feelings of isolation, founders and top executives are stepping outside of the office to focus on improving their well-being. Toms founder Blake Mycoskie struggled with depression and loneliness after scaling his once-small shoe business into a billion-dollar behemoth. Feeling disconnected from his life's purpose and that his “reason for being now felt like a job,” he went on a three-day men's retreat to work on his mental health. And Seth Berkowitz, the founder and CEO of $350 million dessert giant Insomnia Cookies, cautions bright-eyed entrepreneurs the gig “is not really for everyone.”

“It can be lonely; it's a solitary life. It really is,” Berkowitz recently told Fortune.

Brian Chesky, cofounder and CEO of Airbnb

Airbnb's cofounder and CEO Brian Chesky is one the most outspoken leaders in the business world waving the red flag on loneliness. Chesky described having a lonely childhood, pulled between his love for creative design and sports, never really fitting in. But his mental health took a turn for the worse once assuming the throne as Airbnb's CEO. His other two cofounders---who he called his “family,” spending all their waking hours working, exercising, and hanging out together---were suddenly out of view from the peak of the C-suite.

“As I became a CEO I started leading from the front, at the top of the mountain, but then the higher you get to the peak, the fewer the people there are with you,” Chesky told Jay Shetty during an episode of the On Purpose podcast last year. “No one ever told me how lonely you would get, and I wasn't prepared for that.”

Chesky recommends budding leaders actually share their power, so no one shoulders the mental burden of entrepreneurship alone.

“I think that ultimately, today, we're probably living in one of the loneliest times in human history,” Chesky said. “If people were as lonely in yesteryear as they are today, they'd probably perish, because you just couldn't survive without your tribe.”

Indra Nooyi, former CEO of PepsiCo

Leaders at Fortune 500 giant PepsiCo face constant pressure from consumers, investors, board members, and their own employees. But it's also tough to vent to peers who may not relate to---or even understand---the trials and tribulations of running a $209 billion company. Indra Nooyi, the business' former CEO, said she often felt isolated with no one to confide in.

“You can't really talk to your spouse all the time. You can't talk to your friends because it's confidential stuff about the company. You can't talk to your board because they are your bosses. You can't talk to people who work for you because they work for you,” Nooyi told Kellogg Insight, the research magazine for Northwestern's Kellogg School of Management, earlier this year. “And so it puts you in a fairly lonely position.”

Instead of divulging to a trusted friend or anonymously airing out her frustrations on Reddit, Nooyi looked inward. She was the only person she could trust, even if that meant embracing the isolation.

“I would talk to myself. I would go look at myself in a mirror. I would talk to myself. I would rage at myself. I would shed a few tears, then put on some lipstick and come out,” Nooyi said. “That was my go-to because all people need an outlet. And you have to be very careful who your outlet is because you never want them to use it against you at any point.”

Carol Tomé, CEO of UPS

Before Carol Tomé stepped into the role of the CEO of UPS, she was warned the top job goes hand-in-hand with loneliness. The word of caution didn't phase her---at least, not at first. But things changed when she actually took the helm of the $75 billion shipping company.

“I would say, 'How lonely can it really be? It can't be that lonely?' What I've since learned is that it is extraordinarily lonely,” Tomé told Fortune last year.

“When you are a member of an executive team, you hang together...Now, my executive team will wait for me to leave a meeting so that they can debrief together. It's the reality and you have to get used to it. But it is super lonely.”

Tim Cook, CEO of Apple

Apple CEO Tim Cook isn't immune to the loneliness that often comes with the corner office. More than 14 years into his tenure, he's acknowledged his missteps, which he called “blind spots,” that have the potential to affect thousands of workers across the company if left unchecked. Cook said it's important for leaders to get out of their own heads and surround themselves with bright people who bring out the best in them.

“It's sort of a lonely job,” Cook told The Washington Post in 2016. “The adage that it's lonely---the CEO job is lonely---is accurate in a lot of ways. I'm not looking for any sympathy.”

Seth Berkowitz, founder and CEO of Insomnia Cookies

Entrepreneurship can be a deeply fulfilling and rewarding journey: an opportunity to trade a nine-to-five job for a multimillion-dollar fortune, if all the right conditions are met. And while Insomnia Cookies' Seth Berkowitz loves being a CEO and all the responsibilities that come with it, he cautioned young hopefuls about the weight of the career. He, like Cook, advises aspiring founders to counter loneliness with genuine, meaningful connections.

“It can be lonely; it's a solitary life. It really is. [During] the harder times, it's very solitary---finding camaraderie, mentorship, some sense of community, it's really important,” Berkowitz recently told Fortune. “Because I go so deep, it's sometimes hard to find others and let them in.”