According to ScienceAlert, a new study analyzing data from 10,588 young people has found that owning a smartphone at age 12 is linked to increased health risks. The research, led by child and adolescent psychiatrist Ran Barzilay from the Children’s Hospital of Philadelphia, found that at age 12, 6.5% of phone owners had a depression diagnosis versus 4.5% without phones. For obesity, the rates were about 18% versus 12%, and 47% of phone-owning 12-year-olds reported insufficient sleep (less than nine hours) compared to 31% of their peers. The study, part of the ongoing Adolescent Brain Cognitive Development (ABCD) Study, also tracked kids to age 13, finding those who got a phone were more likely to report mental health issues and poor sleep a year later, though obesity risk didn’t change significantly in that short window.
Correlation Isn’t Causation, But…
Now, the big caveat everyone jumps to: this is an observational study. It can’t prove the phone caused the depression or obesity. It just shows a strong association. And the researchers admit there are nuances—like the fact that a depression diagnosis could have occurred before the kid got the phone. So maybe kids who are already struggling are more likely to be given a device? It’s a classic chicken-or-egg problem.
But here’s the thing. The strength of the associations is hard to ignore, especially the sleep data. Nearly half of 12-year-olds with phones aren’t sleeping enough. That’s a massive red flag on its own, because we know poor sleep is a direct pipeline to worse mental health, poorer school performance, and, yes, weight gain. The study also factored in demographics and socioeconomic status, trying to isolate the phone’s role. So while it’s not a smoking gun, it’s a pretty compelling piece of evidence that we should stop treating smartphones as harmless toys for tweens.
The Bigger Picture and What’s Next
Barzilay is careful to note that smartphones aren’t all bad. For many teens, they’re a lifeline for social connection, learning, and safety. That’s the tricky trade-off parents are facing. The device that keeps your kid safe and connected is also the same one that might be keeping them up all night and feeding into a negative feedback loop.
So what do we do with this info? The researchers say the next steps are to dig into the “how.” How much screen time is the tipping point? Do certain types of apps (social media vs. educational games) drive these outcomes differently? And what countermeasures actually work? Barzilay emphasizes that time away from the phone for physical activity is non-negotiable. It’s a basic, but crucial, protective factor. Future research from the ABCD study will hopefully give us more granular answers.
A Shift in Thinking
Basically, this study is part of a growing body of evidence asking us to reframe the smartphone. It’s not just another piece of consumer electronics. For a developing brain, it’s an environmental factor—almost like diet or exercise. We wouldn’t hand a 12-year-old unlimited access to junk food and no bedtime. Yet we often hand them a pocket-sized supercomputer with the same lack of guardrails.
The call from experts like Barzilay is for more intentionality. Approach the decision like you would any other significant health choice for your child. Look at the data, weigh the pros and cons for your family’s situation, and if you do hand over the device, set clear boundaries from day one. Because the stats, while not definitive, are telling a story we probably should have been listening to sooner. You can read more about the study’s findings directly from the Children’s Hospital of Philadelphia.
