Background: Avoidant restrictive food intake disorder (ARFID) is a feeding and eating disorder, characterized by limited variety and/or quantity of food intake impacting physical health and psychosocial functioning. Children with ARFID often present with a range of psychiatric and somatic symptoms, and therefore consult various pediatric subspecialties; large-scale studies mapping comorbidities are however lacking. To characterize health care needs of people with ARFID, we systematically investigated ARFID-related mental and somatic conditions in 616 children with ARFID and >30,000 children without ARFID. Methods: In a Swedish twin cohort, we identified the ARFID phenotype in 6-12-year-old children based on parent-reports and register data. From >1,000 diagnostic ICD-codes, we specified mental and somatic conditions within/across ICD-chapters, number of distinct per-person diagnoses, and inpatient treatment days between birth and 18th birthday (90 outcomes). Hazard ratios (HR) and incidence rate ratios (IRR) were calculated. Findings: Relative risks of neurodevelopmental, gastrointestinal, endocrine/metabolic, respiratory, neurological, and allergic disorders were substantially increased in ARFID (e.g., autism HR[CI95%]=9.7[7.5-12.5], intellectual disability 10.3[7.6-13.9], gastroesophageal reflux disease 6.7[4.6-9.9], pituitary conditions 5.6[2.7-11.3], chronic lower respiratory diseases 4.9[2.4-10.1], epilepsy 5.8[4.1-8.2]). ARFID was not associated with elevated risks of autoimmune illnesses and obsessive-compulsive disorder. Children with ARFID had a significantly higher number of distinct mental diagnoses (IRR[CI95%]=4.7[4.0-5.4]) and longer duration of hospitalizations (IRR[CI95%]=5.5[1.7-17.6]) compared with children without ARFID. Children with ARFID were diagnosed earlier with a mental condition than children without ARFID. No sex-specific differences emerged. Interpretation: This study yields the broadest and most detailed evidence of co-existing mental and somatic conditions in the largest sample of children with ARFID to date. Findings suggest a complex pattern of health needs in youth with ARFID, underscoring the critical importance of attention to the illness across all pediatric specialties. Funding: Fredrik and Ingrid Thurings Foundation, Mental Health Foundation.

Henrik Larsson has received grants from Shire/Takeda; personal fees from Medici, Evolan, and Shire/Takeda outside the submitted work; and is Editor-in-Chief of JCPP Advances. Cynthia M. Bulik receives royalties from Pearson outside the submitted work. Lisa Dinkler has received personal fees from Baxter Medical AB and Fresenius Kabi AB outside the submitted work. All other authors did not report any biomedical or financial conflicts of interest.

Marie-Louis Wronski was supported by the Endocrine Society (REGMS program/Research Experiences for Graduate and Medical Students); the Else Kroener-Fresenius Foundation (structured doctoral program); and the German National Academic Scholarship Foundation. Cynthia M. Bulik was supported by NIMH (R56MH129437; R01MH120170; R01MH124871; R01MH119084; R01MH118278; R01MH124871); Swedish Research Council (Vetenskapsradet, award: 538-2013-8864); Lundbeck Foundation (Grant no. R276-2018-4581). Lisa Dinkler was supported by the Swedish Mental Health Foundation (Fonden foer Psykisk Haelsa); and grant 2021-00660 from the Fredrik and Ingrid Thurings Foundation. The funders had no role in the design/conduct of the study, data management/analysis, or manuscript preparation.

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The study was conducted in accordance with the Helsinki Declaration. The Regional Ethical Review Board in Stockholm, Sweden (Dnr 03-672, 2010/597-31/1, 2010/322-31/2) gave ethical approval for this work. Informed assent was obtained from all human subjects in this study.

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