The constant connection to mobile phones, laptops, and tablets may cause short-term and long-term physical and mental health problems.

A 3-year-old lives in the center of a “me” universe, and most of the time it’s pretty darn cute.

But if she acts the same way at 23, her “me-centered” outlook might be related to her Facebook behavior — and narcissism is usually not cute.

A 2012 study out of Western Illinois University investigated the relationship between two aspects of narcissism — grandiose exhibitionism and entitlement/exploitativeness — and Facebook behavior.

Both aspects indicate a person who probably doesn’t work well with others.

Those who scored high on a test for grandiose exhibitionism tended to use Facebook for self-promotion, such as frequently updating statuses and posting photos.

Those who showed high levels of entitlement/exploitativeness were more likely to react angrily to critical comments and fail to support their friends. In other words, they exhibit antisocial Facebook behaviors.

A similar problem involving attention span emerged in a 2013 study from the University of Massachusetts Amherst, which surveyed 6.7 million internet users.

Researchers found that viewers tend to abandon online videos if they take more than 2 seconds to load, indicating that as technology moves faster, our patience grows thinner.

Read more: Why millennials are having less sex than generation X »

It’s not hard to find examples of how technology is negatively affecting millennials, the most digitally connected population in history.

Their constant connection to smartphones, laptops, and tablets may cause both short- and long-term health problems.

The U.S. Census Bureau says there are now 83.1 million people between the ages of 18 and 34 in the nation.

At least one study concluded the average millennial spends up to 18 total hours per day using digital media. Some of that usage is simultaneous.

In addition, 90 percent of young adults use social media. That’s up from 12 percent in 2005, the Pew Research Center reports.

What does that mean in the long term?

Many of the generation’s young minds are still developing. Scientists at the National Institute of Mental Health say the human brain continues to mature until age 25.

Although research in brain development among millennials is still new, some medical experts say the brains of people in this generation are physically developing differently because of their almost constant interaction with technology. These changes could have an impact on millennials’ communication skills.

Technology use can affect the parts of the brain that control the core of a person’s personality, from how they work in a team down to hand gestures and expressions, according to a story on

“I think it’s very possible” that technology alters the brain, Kirk Erickson, Ph.D., principal investigator of the Brain Aging & Cognition Health Lab at the University of Pittsburgh in Pennsylvania, told Public Source. “But we haven’t yet directly linked these things.”

Brain development is not a one-size-fits-all proposition. Texting and surfing the web use different parts of the brain than reading or speaking.

Some neuroscientists have targeted which parts of the developing brain are affected by technology use. Researchers at the Chinese Academy of Sciences in Beijing say there are changes in the ways the prefrontal cortex, cerebellum, and parietal lobe mature.

The prefrontal cortex, which resides in the frontal lobe, controls personality, cognition, and social behavior. The cerebellum coordinates and regulates muscular activity, including those linked to language. The parietal lobe deals with interpreting language and words.

Excessive use of technology, according to leading scientific publications, atrophies the frontal lobe, breaking down ties between different parts of the brain. Too much technology use also shrinks the outermost part of the brain, making it more difficult to process information.

Erickson told Public Source this can affect the way people interact.

“You might see changes in your ability to regulate emotions, your ability to remember certain events, your ability to pay attention to different things,” he said. “These things all together will certainly affect how you communicate with people.”

“Many of the millennials who are either college age or in the workforce are looking at screens constantly,” Dr. Mark Jacquot, vice president, clinical director, and vision care operations at LensCrafters, told Healthline. “Of course, we’re all glued to our phones right now.”

Read more: How millennials are revolutionizing agriculture »

The long-term effects of heavy technology use are unknown, but millennials are already showing signs of digital wear and tear.

Health problems such as neck and back pain, nearsightedness, and difficulty with offline relationships are increasingly common in this generation.

According to a study by The Vision Council, which represents the manufacturers and suppliers of the optical industry, more than 60 percent of adults spend five or more hours on electronic devices each day. Nearly 4 in 10 millennials, though, log at least nine hours of screen time every day.

“Tech neck” is one of the most noticeable effects of using a cell phone or smartphone for long periods of time. Over time this poor posture can increase wear and tear on the spine. More severe cases could require corrective surgery down the road.

Health professionals blame the rise in back problems among young people on the amount of time they spend sitting at a desk — often in front of a computer screen — and not exercising.

This kind of sedentary lifestyle can lead to other physical problems as well.

“The obvious one is weight gain. You have a lot of increase in weight related to inactivity,” licensed clinical psychologist Lisa Strohman, J.D., Ph.D., founder and director of the Technology Wellness Center, told Healthline.

Research has found that internet addiction — such as playing online games for 10 to 12 hours a day — may rewire certain brain structures, as well as cause brain matter to shrink.

“There are issues around the amount and intensity of how they’re reacting to things — their emotional regulation,” said Strohman. “That’s something that I see in my 20- or 30-year-olds [clients] now that I had never seen before.”

Part of the problem is that over time our moods can become dependent on technology. Playing a game on your smartphone gives you a rush by stimulating the pleasure centers of your brain.

But it can easily go the other way, leading to excessive aggression or a loss of interest in your offline life.

Read more: Why millennial parents are secretive about their babies’ names »

Not everybody is aboard the gloom-and-doom express.

Heavy technology use might actually help with communication, S. Shyam Sundar, Ph.D., a professor in the Penn State College of Communications, and co-director of the Media Effects Research Laboratory, told Public Source.

Sundar said the idea that millennials are bad at picking up emotional cues and can’t talk face-to-face is dated.

“I think we’ve come a long way from that,” he said. “In [a] sense, we are actually able to communicate more richly.”

Technology lets people constantly keep in touch, he said, regardless of age or geography.

“They feel like they’re in the same frequency because of constant communication,” Sundar said.

Communication norms may even change with this new generation. Although face-to-face interaction seems to be the “gold standard” among older generations, he said it might not be viable in the future.

“Millennials might not even think about face-to-face as the ideal,” Sundar said. “Face-to-face might almost be an inconvenience and somewhat pointless.”

This story was originally published on May 4, 2015, and was updated on August 23, 2016.