Interoceptive mechanisms of body image disturbance in anorexia nervosa: Study protocol of a randomized parallel-group trial

Background: Current treatments for anorexia nervosa (AN), a dangerous psychiatric disorder, show only moderate efficacy. Interoceptive processing dysfunctions (i.e., how the brain receives and processes body afferents), and body image disturbance (BID) are clinical features of AN. Floatation-REST (Reduced Environmental Stimulation Therapy) has been reported to enhance both subjective interoceptive experiences and BID. The proposed project works to establish (1) how interoceptive processing dysfunctions may contribute to BID and (2) how the combination of Floatation-REST with psychotherapeutic principles may enhance interoceptive processing and BID in AN. Methods: In this randomized parallel-group ( NCT06332963 ), single-site trial, 102 women and girls with AN will be recruited from an inpatient program. After completing baseline measurements, participants are randomized on a 1:1 ratio to receive either the interoceptively focused treatment (IFT) or exteroceptively focused treatment (EFT) condition. Both conditions utilize acceptance- and mindfulness-based principles, however incorporate skills that focus on interoception or exteroception, respectively. Participants complete acute measures following each experimental therapeutic session, as well as post intervention, six-week and six-month follow-up. The primary outcome of the current study is acute changes in BID assessed by the Photographic Figure Rating Scale. Additional outcomes include acute changes in interoception, and longitudinal intervention effects on self-reported, behavioral, and neuroimaging measures of AN symptoms, BID, and interoception. Discussion: If interventions demonstrate reductions in BID, mechanisms of BID will be further understood, informing the development of future therapies for BID in AN.