Having a smartphone at age 12 is associated with more eating disorder symptoms two years later.
Researchers followed 8,957 American adolescents participating in a large study on youth development. At age 12, about 70% had their own smartphone. The team then compared several eating-related behaviors and concerns among owners and non-owners.
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The symptoms studied do not necessarily correspond to a diagnosed eating disorder. They included binge-eating episodes, certain behaviors intended to prevent weight gain, and strongly basing one's self-esteem on one's weight.
Two years later, adolescents who had owned a smartphone at age 12 more often showed several of these symptoms. After adjustment for various factors, the risk of reporting at least one symptom was 49% higher. The association reached 67% for binge-eating episodes and 50% for certain compensatory behaviors.
The study also took into account whether or not the same symptoms were present at age 12. This helps determine whether the association is based solely on differences that were already present at the start of the follow-up. The researchers also adjusted their calculations for several family and demographic characteristics.
However, these results do not prove that smartphones cause these behaviors. Families who give their child a phone earlier may differ from others in many difficult-to-measure ways. Other factors may therefore explain part of the observed association.
The smartphone itself encompasses many different uses. Social media, videos, games, messaging, and Internet browsing do not expose adolescents to the same content. The study focused mainly on device ownership and cannot identify precisely which activity might contribute to the association.
Several mechanisms could be studied. The authors specifically mention exposure to social media, sleep, and concerns about body image. Each could play a different role depending on how long the device is used, what content is viewed, and how the young person interacts with others.
Future research will need to track more precisely when an adolescent receives their first smartphone and how their usage changes afterward. This approach will help determine whether the appearance of certain symptoms truly follows the acquisition of the phone and which uses are most strongly associated.