It has been widely noted that Donald Trump is a man of bad character: a bullying narcissist with a shaky connection to truth. It has also been widely noted that Trump is addicted to social media — in his case, Twitter.

Could the two be connected?

Bad character is as old as mankind, of course; the Internet is considerably younger. Where human behavior is concerned, however, things can always get worse. What the digital revolution has done for commerce, research, and navigation has been wondrous. But its impact on civil society and social interaction has been poisonous.

This is not an original observation, but some of the people making it might surprise you.

Former Facebook executive Chamath Palihapitiya told business students at Stanford last month that he feels “tremendous guilt” for his role in developing the global social network. “We … created tools that are ripping apart the social fabric of how society works,” he said. “The short-term, dopamine-driven feedback loops that we have created are destroying how society works. No civil discourse; no cooperation; misinformation; mistruth.”

A few weeks earlier, another digital pioneer — Facebook’s founding president, Sean Parker — expressed similar worries. Social media sites grew powerful by “exploiting a vulnerability in human psychology,” Parker said. They were designed to “consume as much of your time and conscious attention as possible” — to get users hooked on Internet sharing that grows more irresistible with each new comment, “like,” and retweet. Parker too spoke of the brain chemistry that makes Facebook, Instagram, Snapchat, Twitter and similar platforms so addictive: the “little dopamine hit” of pleasure that people experience when they talk about themselves.

The Internet didn’t invent the human propensity for self-disclosure or the neurochemistry that rewards it. But smartphones and social media put it on overdrive.

In face-to-face conversation, people devote 30 to 40 percent of their speech to communicate personal feelings or experiences, Harvard researchers found in a 2012 study. On social media, the figure soars to 80 percent. Interactions on social sites thus trigger a dopamine rush far more consistently than traditional communication — and getting that rush requires less effort. Click a button, upload a selfie, fire off a tweet, share a post: Digital media get the brain to release the chemical reward we subconsciously crave as no previous communication format ever has.

In so doing, sites like Facebook are normalizing unhealthy behavior with alarming speed. Most obviously, they promote a culture of relentless narcissism and a persistent hunger for flattery.

“Fifteen years ago,” writes Taylor University professor Zack Carter in Psychology Today, “if you were to take your Nikon CoolPix camera … and begin taking photographs of yourself, sending them to your friends and family every day, you’d be labeled some sort of a lunatic.” But with the spread of smartphones, selfie culture has become ubiquitous. The obsessive posting of self-images has turned millions of Internet users into the paparazzi of their own celebrity.

Likewise the compulsive sharing of every stray thought and banal activity.

“Twitter is the medium of Narcissus,” laments technology critic Nicholas Carr in Utopia Is Creepy, his newest book. “Not only are you the star of the show, but everything that happens to you, no matter how trifling, is a headline, a media event, a stop-the-presses bulletin.” With each dopamine squirt, social media reinforce the desire to keep coming back for more.

A disturbing paradox of social networking is the way it turns isolation into a distortion of community: fake society. “Being online means being alone,” Carr remarks, “and being in an online community means being alone together.”

That is not a prescription for social or emotional health. Fueled by the need for stimulus, appealing to an attention span that keeps shrinking, the fake social media community treats its members harshly, with constant eruptions of public shaming and anger and divisiveness. Facebook and its ilk exacerbate the innate tendency to see other people’s grass as greener (and other people’s selfies as more attractive). Surveys routinely find that large swaths of social media users feel unhappy and inadequate when they compare themselves to others. But they’re addicted to those dopamine shots, and keep coming back for more.

Not surprisingly, the generation that has grown up with smartphones and social media is the one paying the heaviest price.

Young people born since 1995 — the cohort that psychologist Jean Twenge calls iGen — are less independent and more emotionally vulnerable than the generations that preceded them. Poring through the data, Twenge finds iGen teens to be unusually lonely and dislocated. Since 2011, she reports, large national surveys of college and high school students document sharp growth in loneliness and depressive symptoms, and marked declines in feelings of happiness and life satisfaction.

“The results could not be clearer,” writes Twenge. “Teens who spend more time than average on screen activities are more likely to be unhappy, and those who spend more time than average on nonscreen activities are more likely to be happy.” Is it any wonder that many Silicon Valley chieftains send their kids to schools that make a point of not using the Internet?

Like the president, tens of millions of Americans are addicted to their smartphones and social media feeds and have no intention of giving them up. My hunch is that that will change — but only gradually, as the damage we’re doing to ourselves becomes undeniable. Not so long ago, mainstream America smoked cigarettes. Eventually most Americans kicked the habit.

Nicotine lost its grip. Let’s hope dopamine will too.

Jeff Jacoby is a columnist for The Boston Globe.