Smartphones study ties age 12 ownership to eating risks

Smartphones at age 12 were linked to more eating disorder symptoms by age 14 in a U.S. study of nearly 9,000 adolescents. Timing matters.

Age 12 phone ownership

The research, published Friday in JAMA Network Open, used data from the Adolescent Brain Cognitive Development Study, a long-running project tracking brain development and health in American children. Researchers examined whether having a personal smartphone at 12 was associated with eating disorder symptoms reported two years later.

About 70% of 12-year-olds in the dataset owned their own phone, according to the study. Among that group, 24% reported at least one eating disorder symptom at age 14, compared with less than 16% of adolescents who did not have a smartphone at 12.

The paper does not show that smartphones caused the symptoms. It does, however, shift part of the screen-time debate from how long children use devices to when they first get independent access.

Appearance content in a pocket

Dr. Jason Nagata, the study's lead author and an associate professor of pediatrics at the University of California, San Francisco, said early ownership can change the content children encounter. "A smartphone can put a world of appearance-focused content in a young person's pocket," he said.

Nagata said the issue is not only the device itself, but the access it creates to images, messages and social comparison. The tween years are a sensitive period for that exposure, as puberty changes children's bodies and can make body image a larger part of daily life.

Before smartphones and social platforms, those comparisons were more likely to involve classmates or friends. Nagata said comparisons with influencers whose images are curated, edited and filtered can contribute to body dissatisfaction and lower self-esteem, both of which are recognized risk factors for eating disorders.

Disordered eating baseline

Research estimates cited in the report put signs of disordered eating at around 22% among children and adolescents worldwide. Disordered eating is broader than a diagnosed eating disorder and can include fixation on food or weight, distorted body image, restricted eating, vomiting after eating or excessive exercise to offset calories.

The study also found narrower behavioral differences among children who owned phones at 12. They were twice as likely to connect their self-worth to their weight and 1.5 times more likely to have tried to control weight through steps such as eating low-calorie foods or exercising heavily, according to the researchers.

Those figures add a measurable frame to a parental decision that is often treated as a question of convenience or safety. For pediatricians, schools and families, the study points to phone timing as one possible screening question when children show anxiety around food, body shape or weight.

Parents face timing choice

If families delay personal smartphone ownership past age 12, the mechanism would be narrower independent access to appearance-focused feeds during early puberty. That path could reduce one channel of exposure, though children may still encounter similar content through shared devices, friends' phones or computers.

If children receive smartphones in middle school, the study suggests the next layer of risk management is not only screen-time limits. Parents may need to discuss filtered images, influencer content and weight-related messages before the phone becomes a private portal.

If later research reproduces the association, phone makers, social platforms and app stores could face more pressure to strengthen youth defaults around beauty filters, diet content and recommendation systems. The main open question is whether age at first phone ownership remains linked to symptoms after accounting for family environment, prior mental health and offline peer pressure.