Cognitive Behavioural Therapy for Avoidant/Restrictive Food Intake Disorder (CBT-AR)

CBT-AR describes an adaption of cognitive behavioural therapy for use with individuals diagnosed with Avoidant/Restrictive Food Intake Disorder (ARFID). The purpose of this evaluation is to determine the feasibility, acceptability and effectiveness of this treatment. It is hypothesised that this treatment will be feasible and acceptable to clinicians, carers and patients and will be effective in reducing symptoms of ARFID for patients.

CBT-AR describes an adaption of cognitive behavioural therapy that is appropriate for use with individuals diagnosed with Avoidant/Restrictive Food Intake Disorder (ARFID). This therapy will be delivered by trained clinicians (e.g. psychologists, mental health nurses) and involves weekly sessions for 18-30 sessions (up to 30 sessions for underweight patients). This therapy will be delivered face-to-face whenever possible. If required (participant not able to travel for a session etc.) online or telephone sessions will be conducted. This therapy involves four stages as described below. * Stage 1 - Psychoeducation: This is covered in 2-4 sessions and involves explaining what ARFID is, educating patients and carers on food groups, nutrition and how to develop a balanced diet. Work is also done to increase eating volume for those who are underweight. * Stage 2 - Treatment planning: This is covered in 2 sessions and involves matching the individuals needs to the correct exposure approach (examples provided in stage 3). * Stage 3 - Graded exposure is covered for between 12 and 22 sessions (depending on the patient's needs) and describes slowly introducing more variety and volume of foods into the patient's diet. For those patients who are uncomfortable with strong tastes and textures, graded exposure might involve eating very small amounts of new foods during which time they are encouraged to describe the look, feel and taste of the food using neutral words to reduce a negative response. If they have a fear of choking, they might start by talking about that fear, followed by watching a video of someone choking and recovering, then they might eat a very small amount of food to reduce the risk of choking, followed by increases in portions over time. * Stage 4 - Relapse prevention: This is covered in 2 sessions. In these sessions, individuals are taught to recognise triggers and indicators of relapse. They are then able to go back to the materials provided in treatment to guide their management of these relapsing thoughts/behaviours. Clinicians will collect data on adherence weekly. A measure of patient, parent/guardian and clinician satisfaction will be collected at the end of stage 4. Parents/guardians of individuals \<16yrs, or parents/guardians of patients who are underweight and living at home irrespective of age are involved in therapy through attending psychoeducation sessions and supporting the completion of homework.

Inclusion Criteria: * Current primary diagnosis of ARFID according to DSM-5 criteria as determined by the treating team (the eating disorders Orygen Specialist Program * Presenting for treatment in the eating disorders Orygen Specialist Program * If \<16yo, or \>16 but underweight (BMI \<18.5) and living with their parents/guardian, a parent/guardian should be involved in the treatment. Exclusion Criteria: * Current tube feeding * Inappropriateness for CBT-AR as determined by the clinicians (e.g. if there are more urgent issues to first manage such as high suicidal ideation, if participants do not have adequate comprehension capability, etc)