Factor Structure and Measurement Invariance of the Farsi Version of the Nine-Item Avoidant/Restrictive Food Intake Disorder Screen (F-NIAS): Age, Sex, Weight, and Urbanization Group Differences in Disorder Risk Among Adolescents.

Avoidant/restrictive food intake disorder (ARFID) symptoms are prevalent among adolescents, yet no validated scale exists for Iran. This study evaluated the factor structure, measurement invariance, and prevalence of ARFID symptoms among adolescents at high risk for ARFID using the Farsi Nine-Item Avoidant/Restrictive Food Intake Disorder Screen (F-NIAS). Following translation and back-translation, 1,243 adolescents (75.9% girls) completed the F-NIAS. Confirmatory factor analysis confirmed the original three-factor structure with a good model fit. The scale demonstrated measurement invariance across sex, age, weight status, and residency, ensuring consistent performance across groups. Girls and younger adolescents showed higher ARFID symptoms than boys and older adolescents. Adolescents with average body mass index were more likely than those with higher weight to screen at high risk based on picky eating. Urban adolescents reported more low appetite-related restrictions. The F-NIAS is a valid scale for assessing ARFID symptoms in Iranian adolescents at risk for ARFID.