If the most popular person on Instagram doesn’t have many friends, then who really does?

Selena Gomez reigns as the Insta queen with more than 100 million followers. But the 25-year-old singer revealed in an interview this week that she only has a few close friends – like the heroic bestie who donated a kidney to her recently as she battles lupus.

“I have like three good friends that I can tell everything to,” Gomez told Business of Fashion. “And it feels great to be connected to people, but having boundaries is so important. You have to have those few people that respect you, want the best for you and you want the best for them.”

Posh designer Victoria Beckham also told Elle UK in April that, “I don’t have a lot of friends, but I’m surrounded by people I genuinely like to be with.” And Diane Keaton, who was honored with the American Film Institute’s LIfe Achievement Award in a June ceremony where Meryl Streep gave a speech in her honor, told Jimmy Kimmel that, “I don’t really have any friends. Not one.” And as for Streep, “I love her, but I don’t see her very often. She doesn’t call.”

Turns out, even the most famous of us can only truly maintain a handful of close relationships. Oxford anthropologist and evolutionary psychologist Robin Dunbar has calculated that we can only maintain a social network (online and off) of about 150 to 200 people tops – and most of them (100 or so) are really just casual acquaintances that you work with or might invite to a large function, like a wedding. Of those 150, there’s a group of 15 that you confide in or look to for sympathy – but just five make up your inner core of most intimate friends and family.

Yet we tend to think that everyone else has more friends than we do. A new study from the University of British Columbia, Harvard Business School and Harvard Medical School released Thursday found that about half of university freshmen think their coeds have more friends and spend more time socializing than they do – and it’s often not even true. The students consistently overestimated how many friends their peers actually had, and reported lower feelings of well-being and belonging because of it.

“Since social activities, like eating or studying with others, tend to happen in cafes and libraries where they are easily seen, students might overestimate how much their peers are socializing because they don’t see them eating and studying alone,” the study’s abstract stated.

Many of us don’t believe we have as many friends as our peers, research shows. (FangXia/iStockNuo)

And social media is making it worse. “I find evidence that students who spend more time scrolling passively through Facebook are more likely to think that their peers have more friends,” Ashley Whillans, the study’s lead author, told Moneyish. And freshmen are more vulnerable to feeling like outcasts than upperclassmen. “After viewing Facebook profiles with high (vs. low) social content, first year students experience lower levels of belonging as compared to other students,” she said.

Plenty of research has shown that social media makes us unhappy because we compare these perfectly-staged Instagram photos and our peers’ exuberant Facebook posts about getting married and having kids, and despair about how lonely and mundane our own lives look in comparison.

And loneliness is bad for health. Studies have shown it increases mortality risk comparable to smoking. It spurs inflammation and weakens our immune systems, which can lead to arthritis, diabetes and heart disease. It also hurts productivity. A 2011 study found loneliness has ‘significant influence on employee work performance, both in direct tasks, as well as employee team member and team role effectiveness rated by both the employee’s work unit members and supervisor.” And Gallup found workers who don’t have friends at work put in less effort. Surveys have also found a strong correlation between loneliness and work exhaustion or burnout.

So we need to stop worrying ourselves sick thinking that we’re less popular than we really are.

Whillans suggests that employers try “targeted interventions” to help new hires or introverted employees acclimate, such as having more senior workers and leaders mentor them. “[They] share the social challenges that they faced when moving to a new city or when they were new in their workplace, therefore helping to normalize this feeling we all experience of being alone,” she said.

And remind yourself that you’re not so alone after all. “Our research suggests that feelings of loneliness are pretty normal!” Whillans added.