My son, Max, once worked for social media companies. Now he makes his living speaking to students about how phones hook them. He compares smartphones to casino slot machines.

"All the things we love about social media, those are the reward in the slot machine ... we get that 'hit' once in a while ... That's there to keep us scrolling for hours."

Haidt agrees, calling smartphones a "gambling machine."

They say some apps are worse than others.

"Instagram, Facebook, Snapchat, TikTok. Those really shatter attention spans. In terms of exposure to things that are really dangerous, Snap is the worst," says Haidt. "In terms of destroying your ability to pay attention, TikTok is the worst. In terms of destroying a teenage girl's sense of confidence, self-esteem, body image, Instagram is the worst."

He says social media affects boys and girls differently.

"Check in on the kids at age 14, girls are doing worse. They're more depressed and anxious, more messed up."

But a few years later, he says, "Girls are more likely to have gone to college, gotten a job and moved out of their parents' home. Boys are more likely to still be in their parents' basement playing video games. They never grew up. Real life is incredibly boring compared to a video game or porn."

Teachers say phone addiction makes it harder to teach.