Owning a smartphone at age 12 was linked to more eating disorder symptoms at 14 in 8,957 US adolescents

The first phone has become a milestone of late childhood. It tends to arrive somewhere between the last year of elementary school and the start of high school, and parents weigh it against bus journeys, group chats and the fact that everyone else in the class already has one. A large American study adds a consideration that has had little attention: what the timing might mean for how a child comes to feel about food and weight.

Jason Nagata, a pediatrician at the University of California, San Francisco, and colleagues compared 8,957 adolescents who did or did not own a smartphone at age 12. Their paper, published in JAMA Network Open in September, reports that the owners were more likely to describe symptoms of disordered eating two years later. Time spent on screens has been tied to such symptoms before. The age at which a child gets a phone of their own had not, and the authors note that few studies have examined whether it is associated with eating problems in the early teens.

What counts as an eating disorder symptom?

The study did not count diagnoses. At 12 and again at 14, each adolescent answered yes or no to four questions taken from a standard psychiatric interview. One asked about binge eating. One asked about what the paper calls inappropriate compensatory behaviors to prevent weight gain, such as making up for what was eaten by vomiting or exercising hard. The other two asked whether the child worried about gaining weight and whether their sense of self-worth depended on their weight.

A yes to one of these is a long way from an eating disorder. Researchers use the term disordered eating for behaviors and attitudes that resemble an eating disorder without meeting the bar for a diagnosis, and they are common at this age. A 2023 meta-analysis in JAMA Pediatrics, led by José Francisco López-Gil, pooled screening surveys covering 63,181 young people. Its estimate was that the overall proportion of children and adolescents with disordered eating was 22.36%, or more than one in five, with girls affected nearly twice as often as boys.

Symptoms were more common among smartphone owners at 14

The data come from the Adolescent Brain Cognitive Development Study, a long-running federal project that recruited participants from 21 study sites across the US. Parents reported whether their child had a phone of their own and when they got it. By that measure, 6225 adolescents (69.5%) owned a smartphone at 12 years of age.

The raw gap two years on was wide. At age 14, 24.2% of children who had owned a smartphone at 12 reported at least one eating disorder symptom, compared with 15.5% of those who had not. That is about 24 in every 100 against about 16.

Raw gaps mislead when the groups differ, and here they did. Compared with non-owners, the phone owners were more likely to be female, to have lower household income and lower parental educational attainment, and to be further into puberty. Girls and children further into puberty report more disordered eating whatever is in their pocket. The team therefore adjusted for sex, race and ethnicity, family income, parents’ education, puberty, body weight, symptoms of depression and attention problems, how closely parents kept track of their child, and whether the child owned a tablet or laptop. For the two-year comparison they also took into account the symptoms each child had already reported at 12.

A gap survived all of that. Owners were about half again as likely to report any symptom at 14. In the words of one news report on the study, smartphone owners had a 67% higher risk of binge-eating symptoms and a 50% higher risk of inappropriate behaviors meant to prevent weight gain, and about twice the risk of tying their self-worth to their weight.

One of the four symptoms did not follow the pattern. Worry about weight gain was not associated with smartphone ownership in adjusted models, though the authors point out that few children reported it at all, which makes a difference hard to detect.

What a smartphone puts in front of a 12-year-old

Nagata’s explanation starts with what a phone delivers. “A smartphone can put a world of appearance-focused content in a young person’s pocket,” Nagata told CNN. Twelve is also the age when puberty is changing bodies quickly and children are measuring themselves against one another. “But when you’re comparing yourself to influencers whose images are curated, edited and filtered,” Nagata said, “that can lead to more body dissatisfaction and poor self-esteem, and then that can be a risk factor for eating disorders.”

There is independent support for the comparison part of that account. A meta-analysis from the University of Palermo gathered results from 83 studies with 55,440 participants and found a moderate size association between higher online social comparison tendencies and worse body image and eating disorder symptoms outcomes. Most of those studies measured both things at once, which cannot show which came first. An earlier systematic review by Grace Holland and Marika Tiggemann made the same point about its own field, finding that appearance-based social comparison mediated the relationship between social networking and body concerns while concluding that more longitudinal and experimental studies are needed.

The paper raises other routes too, including phones in bed cutting into sleep and a private screen leaving parents less aware of what a child is seeing. The study could test none of them. Its measure was ownership, and the authors acknowledge that smartphone ownership did not capture the content consumed by adolescents or patterns of use.

Where the smartphone finding fits with earlier research

A different team has already examined the same national cohort for other outcomes. Ran Barzilay of Children’s Hospital of Philadelphia and colleagues reported in the journal Pediatrics that, at age 12, smartphone ownership (n = 6739) was associated with higher risk for depression, obesity and insufficient sleep. They also looked at children who had no phone at 12 and got one in the following year. Those children had more mental health symptoms and less sleep at 13 than children who still had none, a difference that held after controlling for baseline mental health and sleep. Two research groups reaching similar conclusions is reassuring up to a point: both drew on the same children.

Nagata’s own group had earlier tied hours of use to the same symptoms. In that analysis, each additional hour of total screen time and social media use was associated with higher odds of every eating disorder symptom measured two years later.

An outside researcher sees the new result as part of a wider pattern. Mitch Prinstein, a psychologist at the University of North Carolina at Chapel Hill who was not involved in the study, told CNN that newer research suggests delaying access to phones and other devices by six months or a year seems to benefit kids’ mental health.

Official positions are moving the same way. According to the paper, professional bodies, including the American Academy of Pediatrics, encourage families to delay and individualize smartphone ownership, and Australia has set a minimum age of 16 years for social media accounts. The study itself offers no threshold. Researchers did not identify a specific age when a child should receive a smartphone.

Who gets a smartphone at 12 was never random

Families chose when to hand over a phone, and that is the weakness that matters most. In the authors’ words, smartphone ownership was not randomized and reverse causation cannot be ruled out. Reverse causation here would mean a child already preoccupied with appearance pressing harder for a phone, so that the worry leads to the device.

Other gaps sit alongside it. The symptoms were reported by the adolescents themselves, which the paper says may be subject to reporting bias. Each was recorded as present or absent, so a single episode and a daily struggle look identical in the data. Bullying, neurodevelopmental conditions and emerging mental health problems can all feed into disordered eating, and these were not accounted for in this analysis. Children left out because of missing data were more often from minority and lower-income families, which limits how far the numbers stretch.

What the study adds is one more outcome to the list of things that travel with an early phone, in a cohort where depression, weight and sleep were already on it. It does not show that holding a phone back would lower any child’s risk. The authors describe eating disorders as serious, potentially life-threatening conditions that are nonetheless often preventable and responsive to early interventions, and concerns about an individual child’s eating are assessed by their doctor.

The study counted symptoms among children who had phones early, and it did not show that the phones produced them.