Do you remember your first smartphone? Perhaps it was a bedazzled Sidekick or even an early iPhone. Whatever it was, it was like a gift from the future—and it’s a milestone kids of today may not even remember. With phones serving as companions for younger and younger kids, there’s rightfully been concern about the impact screen-time has on brain development and attention span.

But, according to a professor of psychology at San Diego State University, parents should be worried about something else entirely: Constant digital contact is linked to a rise in loneliness among adolescents.

Loneliness in the digital age

Jean Twenge is the author of iGen: Why Today’s Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy—and Completely Unprepared for Adulthood—and What That Means for the Rest of Us, published this week. According to Twenge, research indicates today’s kids aren’t as reckless as previous generations were. The bad news is that they are instead more isolated.

The effects of the move from real-life socialization to social media isn’t lost on the kids of today. As one of Twenge’s teenage interviewees put it, it’s as if they like their phones more than they like people. This tendency to socialize through phones has made today’s teens more psychologically vulnerable than Millennials were, Twenge said.

“The Millennials grew up with the web as well, but it wasn’t ever-present in their lives, at hand at all times, day and night,” said Twenge in an excerpt from her book adapted for The Atlantic. “The arrival of the smartphone has radically changed every aspect of teenagers’ lives, from the nature of their social interactions to their mental health.”

More than during any other time in recent history, Twenge said the arrival of the smartphone ushered in “abrupt shifts in teen behaviors and emotional states.”

“It’s not an exaggeration to describe iGen as being on the brink of the worst mental-health crisis in decades,” she said, noting “skyrocketing” rates of teenage depression and suicide since 2011. “Much of this deterioration can be traced to their phones.”

So, what can parents do to help their kids engage with peers offline?

Go low-tech

According to Twenge, we can start by keeping smartphones out of young hands for as long as possible. In an interview with NPR, Twenge suggested kids can still benefit from the safety aspects of cell phones without the smart part.

“If you feel they need a phone, say, for riding a bus, you can get them a flip phone. They still sell them,” she explained.

Discuss trade-offs with kids

Twenge recommended parents talk with kids about the trade-off technology use has, which will help them understand how time online can take away from other experiences they may have socially.

Parents can also encourage and facilitate real-life get-togethers—even those that aren’t naturally “Instagrammable.” Beforehand, it may also help to communicate with the parents of your child’s friends to mutually suggest they put their phones away while hanging out together. (That way there’s no, “But so-and-so’s mom...”)

Institute no-device time

Of course it’s not easy to convince a kid to engage in person when their peers are all on Snapchat and Instagram. In an interview with Metro, technology addiction specialist Dr. Richard Graham suggested parents designate periods of no-device time dedicated to reinstating kids’ interest in things outside their phones.

Or, if they are resistant to that, there are apps that will force them offline for designated amounts of time.

Finally, one of the most important things is leading by example—so parents can start by putting away their own smartphones, too.