This study investigates avoidant/restrictive food intake disorder (ARFID) in a cohort of youth aged 9 to 23 years. The sample includes 100 participants meeting full or subthreshold criteria for ARFID, along with a comparison group of 34 healthy controls, all recruited from the greater Boston area, United States of America. Recruitment was conducted through clinical referrals and community advertisements. Baseline data collection began in 2016, and participants have been assessed at three time points—baseline, one year, and two years—using structured diagnostic interviews to examine illness persistence, remission, and diagnostic crossover.