Aberrant Interoceptive Accuracy in Patients with Schizophrenia Performing a Heartbeat Counting Task

Introduction: Although self-disturbances and emotional disturbances are common in schizophrenia, there is no integrated understanding to explain these symptoms. Interoception has a crucial role in the development of self and emotion, and interoceptive abnormality could lead to such symptoms. Methods: We compared interoceptive accuracy between controls and patients with schizophrenia. Forty-two patients and 30 healthy controls were recruited and their interoceptive accuracy was assessed using a heartbeat counting task. Participants were instructed to count the number of times they felt their own heartbeat during various measurement periods. Interoceptive accuracy was calculated based on the discrepancy between the number of reported and actual heartbeats during the measurement period. Participants also performed a time estimation task and were instructed to count the number of seconds there were during the same period. Time accuracy was calculated in a similar manner to that for the heartbeat. Participants also completed a questionnaire regarding interoception to assess their subjective experiences. Results: Interoceptive accuracy was significantly lower among patients with schizophrenia than in healthy controls (P =. 017), even after controlling for age, sex, time accuracy, anxiety, depression, educational level, and heart rate (HR). In addition, patients' positive and negative symptoms were significantly associated with their HR-adjusted interoceptive accuracy, especially hallucination. The discrepancy between HR-adjusted interoceptive accuracy and the score of the questionnaire was significantly associated with positive symptoms, especially delusion, but not negative symptoms. Discussion: These findings suggest that patients with schizophrenia have aberrant interoception. Aberrant interoception in schizophrenia could be a novel therapeutic target in future.