Why can't we be friends? Lack of social contact harms Americans' mental, physical health.

Recent studies have reported an epidemic of loneliness across the globe. Tragic as this is, we believe it's a symptom of a broader problem. As health professionals trained in medicine and psychology, we see the underlying crisis as a lack of meaningful social connections, or as we call it, a "friendlessness epidemic."

Largely driven by technology, this phenomenon appears to affect younger generations even more than those over 40.

Human beings are social animals. Study after study has found that people who develop close relationships report greater levels of happiness and personal satisfaction. And a high level of daily social interaction is one of the most consistent predictors of psychological well-being.

People with friends are also physically healthier. With lower rates of heart disease, cognitive decline, obesity and other common ailments, social people enjoy longer lives. For those suffering from disease, loneliness has been shown to reduce lifespan.

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Many Americans have no close friends

Yet 12% of American adults say they don't have a single close friend, according to a study by the Survey Center on American Life. Worrisomely, that represents a fourfold increase over the past three decades. In addition, 20% report having only one or two close friends.

For young people, the situation is worse, because many are not developing the skills needed to form friendships. Teens interact with each other in fundamentally different ways than they did just 15 years ago. Those of Generation Z – roughly 10 to 25 years old – are significantly less likely to go to parties, hang out together after school, date, drive around in cars or otherwise engage in face-to-face social interactions than previous generations.

This disconnection is closely tied to a broader crisis in youth well-being. Last year, a coalition of U.S. pediatric groups declared a state of emergency in child and adolescent mental health, which had already been deteriorating.

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From 2009 to 2019, the number of high school students who reported persistent feelings of sadness or hopelessness rose by 40%, to more than 1 in 3. The phenomenon is international: A study in the Journal of Adolescence found that teen loneliness increased in 36 countries between 2012 and 2018.

COVID-19 exacerbated our loneliness. Social distancing, quarantine orders and fear of contagion forced millions to isolate. Many fell out of touch with friends and family. Those who underwent life transitions – such as graduating, starting a job or becoming a parent – lost out on the supportive relationships that normally accompany such changes. The pandemic also increased remote work, which makes it hard to start and maintain friendships with colleagues.

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But dramatic societal changes over the past two decades bear more of the blame for increased friendlessness.

Social media has fundamentally transformed the way we communicate, according to social psychologist Jonathan Haidt – and not just in the most obvious ways. Face-to-face interactions involve give and take, creating a two-way street that allows personal relationships to develop. But social media turns every communication into a public performance. Audience members may respond with likes, reposts or comments, but rarely do so with offers of deeper personal engagement.

Clicks simply don't equate to real human connection.

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Social media has also encouraged two successive generations – millennials, born 1981 to 1996, and Gen Z, born 1997 to 2012 – to spend valuable developmental time watching other people live their lives as opposed to living their own.

This leads to feelings of inferiority, with viewers comparing their real experiences with the embellished or fictionalized lives displayed online.

Smartphones get in the way of human interactions

Meanwhile the smartphone, that great tool of connectivity, also pulls people apart. Sociologist and psychologist Sherry Turkle found that even when conversation partners are physically together, the presence of a phone stops them from fully engaging with each other. Instead, they skate across the surface of discussions.

With a phone at hand, one's attention is always primed for disruption.

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While this dynamic affects people of all ages, it's most damaging to our youth. According to a study published in JAMA Pediatrics, screen time outside of virtual school among teenagers doubled from pre-pandemic estimates of 3.8 hours a day to 7.7 hours.

Many peer interactions now take place exclusively in a virtual sphere. But without in-person experiences, kids aren't learning how to read nonverbal cues or develop other basic interpersonal skills. Without them, adolescents struggle like never before to establish friendships.

Dating apps have also deprived younger generations of important relationship-building tools. In real-life dating, participants progress step-by-step from superficial connection to serious partnership. Along the way, they develop emotional resilience from early-stage romances that end. But dating apps encourage a leap from zero to all-in intimacy, with no opportunity to build inner strength.

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We're deeply concerned that these trends are transforming society for the worse, and that today's epidemic of friendlessness will become permanent.

How do we change?

Transformation can begin at the personal level, with shifts as simple – and as hard – as disengaging from our phones and social media. But our institutions and health care professionals also have a role to play, by facilitating more substantial one-on-one interactions.

Educators can help, too, by creating experiences that require two-way communication and teamwork, and designing curricula that teach the fundamentals of relationship-building, such as how to recognize and acknowledge others' feelings.

If we don't work to form meaningful relationships today, we will be friendless into the future, with negative developmental and health impacts for generations to come.

Phil McGraw, one of the most well-known mental health professionals in the world, is the host of one of daytime TV’s top-rated program, "Dr. Phil." John Whyte is chief medical officer of WebMD.

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This article originally appeared on USA TODAY: Alone again, naturally: Lack of friends hurts Americans' mental health