Children who own smartphones at age 12 are more likely to report eating disorder symptoms two years later than peers without the devices, according to a new study. The research was published Friday in the medical journal JAMA Network Open.

The findings came from a broad survey involving nearly 9,000 adolescents across the United States. Researchers examined whether the age at which children begin using smartphones might be associated with the later development of disordered eating.

“A smartphone can put a world of appearance-focused content in a young person’s pocket,” said lead author Dr. Jason Nagata. He said that access can expose children to images and messages that may encourage unhealthy eating behaviors.

“It’s important for parents to be aware that getting a smartphone isn’t just about the device. It can change a child’s access to different content and exposures in the digital world,” Nagata said.

Nagata is an associate professor of pediatrics at the University of California, San Francisco. He said the timing of smartphone ownership may matter, not merely whether a child eventually receives a phone.

Screen time and social media use have been associated with several negative outcomes among children, including depression, diminished feelings of worth, and experimentation with drugs and alcohol. Previous research from Nagata’s laboratory also found correlations between screen time and binge eating.

Earlier studies have largely examined how much time young people spend using their devices. For the new research, Nagata wanted to concentrate on the age when children start using smartphones and how that timing might relate to disordered eating later.

Research estimates indicate that about 22% of children and adolescents worldwide show signs of disordered eating. The difference between disordered eating and an eating disorder largely involves severity and whether someone meets the criteria for a diagnosis.

Both can involve fixation on food and weight, distorted perceptions of body shape and size, restricted eating, or efforts to compensate for calorie intake through vomiting or exercise. The tween years can be particularly important because puberty brings substantial physical and emotional changes.

Using data from the Adolescent Brain Cognitive Development Study, researchers found that 70% of children age 12 owned a phone. The project is a large study of brain development and health among American children.

Among those who had their own phone at 12, 24% reported at least one eating disorder symptom at age 14. By comparison, less than 16% of teenagers without a smartphone at 12 reported disordered eating two years later.

Children with smartphones at 12 were twice as likely to connect their sense of worth to their weight. They were also 1 ½ times more likely to have attempted weight control through behaviors such as eating foods with fewer calories or exercising heavily.

Nagata said it is natural for children experiencing puberty to compare themselves with one another. Before smartphones and social media, those comparisons occurred mainly among peers, but online platforms can expose children to influencers whose images have been curated, edited and filtered.

“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.”

Dr. Mitch Prinstein, who was not involved in the study, said delaying access to phones and other devices by six months or a year appears to benefit children’s mental health. Prinstein is the John Van Seters Distinguished Professor of Psychology and Neuroscience at the University of North Carolina at Chapel Hill and codirector of the Winston Center on Technology and Brain Development.

Prinstein recommended that parents gradually increase children’s social media access after they receive phones. “We don’t want to give them a completely unlocked phone with all the opportunities to visit whatever they want for as long as they want,” he said.

Most major social media platforms require users to be at least 13 to create an account, Nagata said. However, his previous research found that nearly two thirds of children ages 11 and 12 had accounts on platforms including TikTok and Instagram.

The study does not provide a “magic answer” for the ideal age to give a child a smartphone, Nagata said. Parents who provide phones to preteens could consider additional safeguards, including restrictions on downloadable apps and keeping phones out of bedrooms to make monitoring easier.

“It’s so important for parents to stay involved with their children’s digital lives,” Nagata said. He recommended establishing phone rules, discussing what children encounter online, and watching for changes in eating habits or how children speak about their bodies.

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