Smart phones are now ubiquitous and have revolutionized almost every aspect of our lives in barely less than a decade. The power of digital connectedness, convenience, and information is at our fingertips.

Yet these devices are powerfully addictive. They intrude on our in-person relationships and time spent together, as well as on our attention spans and sense of calm. They provide unrelenting access to stimulation and diversion that conditions us to a heightened mental state.

And now research is beginning to show just how detrimental all this screen time is for the generation of kids that only knows a world with smart phones.

Jean M. Twenge is a psychologist who has been researching generational differences for 25 years. While most changes among generations tend to happen somewhat gradually, she noticed an abrupt shift around 2012, right as smart phones passed the threshold of ubiquity. As she writes in a fascinating and disturbing article in the Atlantic:

Some generational changes are positive, some are negative, and many are both. More comfortable in their bedrooms than in a car or at a party, today’s teens are physically safer than teens have ever been. They’re markedly less likely to get into a car accident and, having less of a taste for alcohol than their predecessors, are less susceptible to drinking’s attendant ills.

Psychologically, however, they are more vulnerable than Millennials were: Rates of teen depression and suicide have skyrocketed since 2011. It’s not an exaggeration to describe iGen as being on the brink of the worst mental-health crisis in decades. Much of this deterioration can be traced to their phones.

And these alarming results are traced clearly to this new technology:

The results could not be clearer: 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.

There’s not a single exception. All screen activities are linked to less happiness, and all nonscreen activities are linked to more happiness.

It shouldn’t be a surprise that increasing physical isolation leads children to unhappiness, combined with the mental blur of interacting via a screen with so much information and social communities. We are basically conducting a massive psychological experiment on today’s children to see how they’ll react to the technology of this brave new world.

To be sure, there are plenty of obvious positives with smart phone usage. As the article points out, kids are safer and engaging in less risky behavior. They also have the opportunity to use the technology to benefit their intellectual and social development.

But these technologies need to be viewed with skepticism. As Twenge concludes, the best advice for a happy adolescence is straightforward:

“Put down the phone, turn off the laptop, and do something—anything—that does not involve a screen.”