ISLAMABAD: Psychologist Jean Twenge says smartphones have brought about dramatic shifts in behavior among the generation of children who grew up with the devices.

For the first time, a generation of children is going through adolescence with smartphones ever-present. Jean Twenge, a professor of psychology at San Diego State University, has a name for these young people born between 1995 and 2012: "iGen."

She says members of this generation are physically safer than those who came before them. They drink less, they learn to drive later and they're holding off on having sex. But psychologically, she argues, they are far more vulnerable.

"It's not an exaggeration to describe iGen as being on the brink of the worst mental health crisis in decades," she writes in a story in The Atlantic, adapted from her forthcoming book. And she says it's largely because of smartphones.

Twenge spoke to All Things Considered about her research and her conclusions. This interview has been edited for length and clarity.

How does teen behavior now differ from generations past?

Today's teens are just not spending as much time with their friends in person, face-to-face, where they can really read each others' emotions and get that social support. And we know from lots and lots of research that spending time with other people in person is one of the best predictors for psychological well-being and one of the best protections against having mental health issues.

What is this generation facing that worries you so much?

iGen is showing mental health issues across a wide variety of indicators. They're more likely than young people just five or 10 years ago to say that they're anxious, that they have symptoms of depression, that they have thought about suicide or have even [attempted] suicide. So across the board, there's a really consistent trend with mental health issues increasing among teens.

Is it specifically the smartphone, or is it social media? Or is it the number of hours per day spent on these things?

So, you look at the pattern of loneliness. It suddenly begins to increase around 2012. And the majority of Americans had a cell phone by the end of 2012, according to the Pew Center.

Given that using social media for more hours is linked to more loneliness, and that smartphones were used by the majority of Americans around 2012, and that's the same time loneliness increases, that's very suspicious. You can't absolutely prove causation, but by a bunch of different studies, there's this connection between spending a lot of time on social media and feeling lonely.