Importance Avoidant restrictive food intake disorder (ARFID) is a newly recognised eating disorder in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition and in the International Classification of Diseases, Eleventh Revision which shows great heterogeneity in its clinical presentation. Objectives Here, we examined the clinical characteristics of ARFID and explored the associations between ARFID symptoms and traits of anxiety. We also investigated whether individuals with ARFID show a different clinical presentation based on their biological sex or comorbid autism spectrum disorder (ASD) diagnosis. Design, Setting, and Participants We recruited 261 consecutive patients from the specialised ARFID outpatient service at the Maudsley Centre for Child and Adolescent Eating Disorders, Michael Rutter Centre, Maudsley Hospital, London, United Kingdom. Main Outcomes and Measures The parents of the patients completed the Pica, ARFID, Rumination Disorder - ARFID - Questionnaire (PARDI-AR-Q), the Revised Children's Anxiety and Depression Scale (RCADS) and reported biological sex of their offspring. Age, height, and weight were obtained from medical records. Clinicians reported on comorbid ASD diagnosis and anxiety traits using the Current View Tool. Results This cross-sectional study included 261 child and adolescent ARFID patients (133 [51%] female) with a median age of 12.7 years (IQR=9.2 to 15.8). Patients' BMI-for-age z-scores ranged from -6.75 to 4.07 (median = -1.07, IQR = -2.25 to -0.01). Patients' comorbid traits of anxiety had the highest correlations with symptoms on the concern about aversive consequences driver of ARFID: panic disorder correlated with physical feelings of panic and anxiety when eating (r=0.53, p=7.74 x 10-31) and being afraid to eat (r=0.42, p=5.13 x 10-21); generalised anxiety correlated with physical feelings of panic and anxiety when eating (r=0.44, p=7.72 x 10-23); and separation anxiety correlated with avoiding eating situations (r=0.36, p=2.01 x 10-15). Sensory sensitivity to the appearance of food positively correlated with separation anxiety (r=0.40, p=1.52 x 10-16) and generalised anxiety (r=0.36, p=7.16 x 10-18). The sensory sensitivities (RR = 0.96; 95% CI, 0.85 to 1.09; P = .53), lack of interest (RR = 1.14; 95% CI, 1.03 to 1.28; P = .02) and concern about aversive consequences (RR = 1.27; 95% CI, 1.03 to 1.56; P = .03) drivers were independent of patient sex. Comorbid ASD was reported in 74 (28%) ARFID patients. Their parents reported higher rates of food-related sensory sensitivities (RR = 1.26; 95% CI, 1.09 to 1.45; P=0.002) and lack of interest (RR = 1.19; 95% CI, 1.05 to 1.34; P=0.006) driving their child's avoidant and restrictive eating than parents of ARFID patients without ASD (127 [49%]). Conclusions and Relevance Our study highlights that ARFID patients present with varying combinations and severity of food-related sensory sensitivities, lack of interest and concern about aversive consequences which drive their avoidant and restrictive eating. ARFID does not discriminate between male and female children and adolescents or those with or without ASD. Anxiety and ASD can co-occur with ARFID, and ASD may accentuate food-related sensory sensitivities and lack of interest. Healthcare professionals should be aware of the multi-faceted and heterogenous nature of ARFID; it is important that comprehensive multidisciplinary assessments are administered to sufficiently understand the drivers of the eating behaviour and associated physical health, nutritional, and psycho-social risk and impact.

The authors have declared no competing interest.

Christopher Hübel acknowledge funding by Lundbeckfonden (R276-2018-4581).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Our study is a clinical audit and was ethically approved by South London and Maudsley Child and Adolescent Mental Health Service Clinical Governance Approval committee on the 3rd of June 2021.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes