From Body to Brain and Back: Multimodal Evidence for Interoceptive Alterations in Schizophrenia Spectrum Disorders

When the brain and body misalign, emotional experience and sense of reality can be disrupted. Although such atypical experiences are central to schizophrenia spectrum disorders (SSD), interoception, processing of internal bodily signals, remains poorly understood in individuals with SSD, particularly across subjective, behavioural, and neural domains. We tested whether SSD is associated with convergent alterations across interoceptive domains and whether these relate to clinical symptoms in a cross-sectional observational design. Patients with SSD (n = 53) and matched healthy controls (HC; n = 60) completed an EEG experiment comprising eyes-closed and eyes-open resting-state recordings and a heartbeat counting task (HCT), followed by self-report measures. Interoceptive accuracy was derived from the HCT, while cortical responses to afferent cardiac signals were indexed by heartbeat evoked potentials (HEP). In individuals with SSD, subjective interoceptive awareness was altered, characterised by impaired regulation and negative bodily appraisal, alongside elevated depersonalization. At the behavioral level, interoceptive accuracy was marginally lower. HEP positivity was attenuated, most clearly during HCT and, to a lesser extent, in eyes-open rest, over centro-parietal regions, consistent with context-dependent alterations in cortical processing of afferent bodily signals. Symptom-interoception links were largely modest, with depersonalization emerging as the most consistent correlate of clinical severity, suggesting that interoceptive disturbances in SSD may reflect a trait-like, disorder-central alteration. Together, these findings indicate that SSD involves pervasive disturbances in bodily self-experience, marked by impaired interoceptive regulation and by context-dependent neural attenuation during interoceptive engagement. This profile highlights interoceptive dysfunction as a disorder-central feature with potential prognostic and therapeutic relevance.