Altered Gastrointestinal Interoception in Anorexia Nervosa Predicts Relapse.

Anorexia nervosa (AN) is a deadly psychiatric disorder, yet relapse remains common after weight restoration and no objective tools exist to track recovery. AN involves profound disturbances of gastrointestinal interoception, but no clinical tests assess this dysfunction. In this single-blind, randomized-crossover study, 62 weight-restored females with restrictive AN and 57 matched healthy comparisons completed a gastrointestinal detection task using an ingestible vibrating capsule while behavioral, electroencephalographic, and peripheral physiological signals were recorded. AN participants showed reduced perceptual accuracy and higher miss-rates despite intact neural and physiological responses. Computational modeling revealed stronger prior beliefs against perceiving gut sensations, diminished interoceptive precision, and maladaptive learning. Capsule stimulation also induced larger hunger increases in AN. Initial priors, response bias, and stomach unpleasantness predicted six-month relapse, while miss-rate and precision shifts predicted symptom severity. These findings reveal mechanistic disruptions in gastrointestinal interoception that predict relapse, offering scalable biomarkers to personalize treatment and prevent recurrence.