Most parents have had the conversation at some point.
The eye-roll from a tween who insists everyone else already has one.
The quiet pressure of lunchroom status and group chats you are not part of.
A new study of nearly 9,000 American adolescents, published in JAMA Network Open, has put a number on what many parents already suspected.
Kids who owned a smartphone at age 12 were 67 percent more likely to show binge-eating symptoms by age 14 than kids who did not.
They were also 50 percent more likely to turn to extreme fasting or purging to control their weight.
And they were twice as likely to tie their self-worth to the number on the scale.
The findings come from the Adolescent Brain Cognitive Development Study, a long-running US project that has followed thousands of children across 21 research sites.
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Nearly 70 percent of the 12-year-olds in the sample already owned their own phone.
Early eating disorder symptoms
Researchers tracked four types of symptom.
Binge eating means putting away a large amount of food in a short time while feeling out of control.
Compensatory behaviors cover vomiting, laxative use or long stretches of skipped meals to undo what was eaten.
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Tying self-worth to weight is harder to spot from the outside.
Parents may notice mood swings around the scale, food being hidden, or constant talk about body shape and dieting.
By age 14, about one in four kids who had owned a phone at 12 reported at least one of these symptoms.
Among kids who did not have a phone at 12, the figure was closer to one in six.
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Why the phone itself may matter
Lead author Dr. Jason Nagata, a pediatrician at the University of California, San Francisco, spoke to ABC7 News.
He said that "having a smartphone can just put a world of appearance focused content in the young person's pocket."
At the age when children start comparing their bodies with those of peers, that content is only a thumb-swipe away.
Reporters covering the study pointed to filtered influencer photos, trends like "looksmaxxing" and ads for weight-loss drugs.
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All of it turns up in the same feeds that carry homework reminders and friend chats.
The study is observational and cannot prove the phone itself causes the symptoms.
The researchers did not capture what the children actually watched or did on their phones, and reverse causation cannot be ruled out.
Even so, the pattern held across the full group of nearly 9,000 kids.
The authors conclude that the timing of when children get a phone may be linked to the risk of eating disorder symptoms during these years.
What parents can do now
The study did not pin down a specific age at which a child can safely own a phone.
Nagata, speaking to Medical Daily, lists several steps.
These include "setting ground rules for phone use, limiting which apps a child can download, keeping phones out of bedrooms and away from the dinner table, and introducing social media gradually."
He also urges parents to talk openly about what their children see online and to watch for changes in how they eat or talk about their bodies.
If those patterns continue, the next step is a conversation with the family pediatrician.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.