A Reddit user revealed in a recent post that as a young person in his mid-20s, he's had a lot of trouble making new friends.

He said he'd kept a "few golden friends" over the years — yet lately he'd been "working so much I hardly noticed that’s all I ever did."

He said that "recently, [while] going through a rough patch in life, I realized I really have no one … to turn to. I’m 25, and I have true friends back home," he added — but "absolutely no one [else]. Isn’t that lonely?"

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This individual's experience is far from isolated. And now, for everyone else having a tough time finding new friends or maintaining long-term relationships, it turns out that science may help. 

"The misconceptions about friendship — I think one of the biggest ones is that friendship should happen organically," Dr. Marisa G. Franco, a psychologist who studies friendship and is based in Washington, D.C., told Fox News Digital.

"Friendship doesn't really happen organically in adulthood," added Franco, a speaker and author of The New York Times bestseller "Platonic: How the Science of Attachment Can Help You Make — and Keep — Friends."

However, science may help break through the difficulties. 

Even before the COVID-19 pandemic began, U.S. Surgeon General Vivek Murthy said that in America, we are in an "epidemic of loneliness." 

One in five Americans said they were lonely or socially isolated — often negatively affecting their health, relationships or work — according to a 2018 study by the Kaiser Family Foundation.

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But the pandemic only worsened the crisis.

Approximately 12% of Americans said they had no close friends in 2021, compared to 3% of Americans in 1990, according to an American Perspectives survey last year.

Many people appreciate that loneliness can worsen a person's mental health — yet it can also weaken physical health as well. 

One study even related the effects of social isolation and loneliness to smoking 15 cigarettes a day, according to a paper by Dr. Julianne Holt-Lunstad, a professor of psychology and neuroscience at Brigham Young University

"We know that healthy relationships are comprised of quality time together, shared vulnerability and interactions that leave both people feeling good," said Shasta Nelson, a San Francisco-based friendship expert and author of "Frientimacy: How to Deepen Friendships for Lifelong Health and Happiness." 

Dr. Franco of Washington, D.C., told Fox News Digital that making friends when we reach adulthood is different from when we were younger.

She explained that adults may end up very lonely "if we expect the same assumption that we made as kids that friendship should just happen organically."

"Sociologists since the 1950s have considered repeated, unplanned interactions in a setting that encourages people to let their guard down and confide in each other as important to the formation of friendships," said Dr. Rebecca G. Adams, professor of sociology and gerontology in the School of Health and Human Sciences at the University of North Carolina, Greensboro. 

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"High schools and colleges are, for example, breeding grounds for friendship because students who attend a given institution usually have a lot in common," Adams told Fox News Digital. 

"As we grow older, it is important to continue to participate in activities that interest us and therefore attract kindred spirits."

She noted that regardless of age, friendships generally start in settings we visit routinely — whether online or face-to-face and whether for fun or practical reasons.

But to "change these relationships from acquaintances into friendships, it is important we make plans to see the friend outside the group setting to get to know each other better," Adams added.

We often decide on "how much to invest in a relationship based on our view of how likely we are to get rejected," which is called the "risk regulation theory," said Franco.

For example, people who think others will reject them will not initiate a lot of friendships, compared to those who are good at initiating friendships because they often assume others will accept them, she added.

"Knowing risk regulation theory means that if we want to make friends, we can make sure we're sending out signals to others that they won't be rejected by us."

This can be a warm smile or introducing yourself when greeting people as examples of an indicator that we will not reject other people — and this, in turn, makes that person more likely to invest in a friendship with us, Franco said.

When strangers interact, they often predict how liked they are by the other person, which is known as the "liking gap."

But people "actually underestimate how liked they are and the more self-critical people are, the more pronounced this liking gap is," Franco said.

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So Franco noted that one of the keys to friendship is to assume other people like you. She refers to this as the "acceptance prophecy."

Franco describes a research project in which people were told by a researcher that they would go into a group and be liked, even though this was a lie. 

"What it did was it made them open, friendlier and warmer — and it became a sort of self-fulfilling prophecy," she added.

"So I think maintaining your friendships also requires you to assume people like you."

Another friendship concept is the "mere exposure effect," based on "the idea that we like people more from merely being exposed to them."

The idea is rooted in a study in which researchers planted women in a large psychology lecture. "By the end of the semester, none of the students remembered any of the women," said Dr. Franco. 

But they liked the woman who showed up for the most classes.

"It's completely unconscious [that] we tend to like people that we've been exposed to more," she added.

This means that when someone joins a new social group, "you should assume that at the beginning, you're going to be wary and distrusting because the mere exposure effect hasn't set in." Yet "over time, you will get more comfortable that you'll like them more — [and] they’ll like you more" as well.

The best advice for maintaining friendships "is to create something repeated over time," Dr. Franco added.

"I did this with my friends. We started a wellness group where I went to one friend and I say, ‘Start by asking one friend and then ask them to lead the group with you.’"

This approach is a lot less intimidating, she said — and eventually it will lead to asking each of the people in the group to bring one other person. "Then you have a group," she said. 

She also recommends taking advantage of social media, such as "liking" the content of others and then eventually private-messaging them.

"You can do it over an email [or] you could do it over Instagram [or] you could Facebook message someone," Franco said.

"I think technology often provides us with this buffer."

She says this decreases our fears of rejection. 

But adults often also feel too busy or tired with day-to-day schedules to maintain friendships, Nelson told Fox News Digital. 

"The part that feels like work for most of us as adults is making that quality time," she added.

She added, "It takes a lot of consistent interaction to stay in touch with each other and keep making memories together."

"Even harder than making time for our friends is making time for new friends," Nelson said.

New friends require "more energy and may not yet feel as meaningful and supportive as a longtime friend."

But even though it’s easy to not invest in new relationships, "we will never feel close to them unless and until we devote that time," she told Fox News Digital.

Franco noted that setting expectations for friendships will decrease conflict and hurt feelings.

Still, friendships often can have unclear expectations, she said. 

So when we say we have a best friend, this "calibrates expectations." 

Also, Franco said that "we can have a quality friendship" with someone who isn't "a best friend."

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Research on friendships shows that generally people "need an entire community to feel whole." She describes those who engage with different types of people to help them process different emotions have "emotion chips" that help them "experience a greater well-being overall."

"The research on loneliness suggests that one person can't fulfill all dimensions of our loneliness and that we need an entire community," said Franco. So there is a "liability" of a best friend.

Although some people are not as social as others, Franco emphasized "the importance of putting yourself out there for people who are not as social."

For example, she suggested trying to reconnect with people from the past.

"The research finds that when you send that reconnection text, people actually appreciate it more than you think," she added.

"So why not just reconnect with someone you've fallen out of touch with — someone that you've really liked — to be able to make more friends?"