Smartphone Ownership and Eating Disorder Symptoms in Early Adolescence.

IMPORTANCE: Adolescents have been owning smartphones at increasingly earlier ages. The associations between age of smartphone ownership and eating disorder (ED) risk among adolescents have not been examined. OBJECTIVE: To examine cross-sectional and longitudinal associations between age of smartphone ownership and ED symptoms in adolescence. DESIGN, SETTING, AND PARTICIPANTS: The Adolescent Brain Cognitive Development (ABCD) Study used a stratified, probability-based sample of schools and recruited participants from 21 study sites across the US. Schools were oversampled based on race, ethnicity, socioeconomic status, and urbanicity to minimize systematic sampling biases in recruitment. Percentages were weighted based on American Community Survey data to represent population estimates. Cross-sectional and 2-year longitudinal analyses applied generalized linear models with a Poisson distribution and log link to ABCD Study data from years 2 to 6 (2018-2024). Data were analyzed from 2025 to 2026. EXPOSURES: Smartphone ownership at 12 years of age (yes or no). MAIN OUTCOMES AND MEASURES: Binge-eating symptoms, inappropriate compensatory behaviors to prevent weight gain, worry about weight gain, self-worth tied to weight, and any ED symptoms were examined separately at 12 and 14 years of age (yes or no). RESULTS: Of 8957 participants (4712 [51.8%] male), 6225 (69.5%) owned a smartphone at 12 years of age. Of 6225 participants, the most prevalent ED symptoms were binge-eating symptoms (315 [9.2%]) at 12 years of age and compensatory behaviors (494 [20.5%]) at 14 years of age. In covariate-adjusted analyses, owning a smartphone at 12 years of age was cross-sectionally associated with a higher prevalence of binge-eating symptoms (prevalence ratio [PR], 1.61 [95% CI, 1.17-2.23]; P = .003), tying self-worth to weight (PR, 2.21 [95% CI, 1.03-4.74]; P = .04), and any ED symptom (PR, 1.36 [95% CI, 1.09-1.70]; P = .007). In covariate-adjusted analyses, owning a smartphone at 12 years of age was longitudinally associated with a higher risk of binge-eating symptoms (risk ratio [RR], 1.67 [95% CI, 1.11-2.52]; P = .01), using inappropriate compensatory behaviors to prevent weight gain (RR, 1.50 [95% CI, 1.16-1.94]; P = .002), tying self-worth to weight (RR, 2.03 [95% CI, 1.28-3.19]; P = .002), and any ED symptom (RR, 1.49 [95% CI, 1.19-1.87]; P < .001). CONCLUSIONS AND RELEVANCE: In this cohort study of US adolescents, smartphone ownership was associated with a variety of ED symptoms, suggesting that the timing of smartphone ownership may be associated with ED risk. Future research is needed to characterize the mechanisms underlying these observed associations.