Reliability and Validity of the Japanese Version of the Inventory of Psychotic-Like Anomalous Self-Experiences

Basic self-disturbance is an abnormality in subjective self-experience and a core feature of schizophrenia. The Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) is a self-report measure designed to assess basic self-disturbance. Despite its clinical utility, a Japanese version has not yet been established. This study aimed to develop a Japanese version of the IPASE and evaluate its reliability and validity.

The study included 182 participants (83 individuals with schizophrenia and 99 healthy controls). The Japanese version of the IPASE was administered to all participants, along with the PANSS and YMRS, to assess validity.

All IPASE domain scores and the total score were significantly higher in the schizophrenia group than in healthy controls. The IPASE total score showed good internal consistency (Cronbach's α > 0.80). In the schizophrenia group, the PANSS positive subscale, general psychopathology subscale, and total scores were all significantly positively correlated with IPASE scores. These positive correlations with the positive subscale support convergent validity. ROC analysis indicated that the IPASE total score had good discriminative ability for schizophrenia diagnosis (AUC = 0.851).

The Japanese version of the IPASE demonstrated high reliability and validity.