Can Self-Disorders Be Self-Rated? Theoretical and Empirical Validity of the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE)

BACKGROUND: The Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) was developed as an easy-to-use, self-report measure of self-disorders. Self-disorders are subtle, trait-like, non-psychotic anomalous self-experiences that are traditionally assessed by trained raters using a semi-structured clinical interview, such as the Examination of Anomalous Self-Experience (EASE). Whether self-disorders can be validly assessed via self-report measures remains uncertain. This study explores the theoretical and empirical validity of IPASE. METHODS: Forty-one participants (patients with psychosis or schizotypal disorder, patients with other mental disorders, and healthy controls) completed the IPASE and were subsequently assessed with the EASE. Correlations between total scores of IPASE and EASE were analyzed using Spearman's ρ, and group differences were examined with one-way ANOVA. Participants were also asked to describe the experiences they had in mind when agreeing with IPASE items, enabling a qualitative comparison of IPASE item interpretation relative to EASE phenomena. RESULTS: Scores on IPASE and EASE were moderately correlated (Spearman's ρ = 0.54, p < 0.01), corresponding to approximately 29% shared variance. While participants with higher EASE scores tended to report higher IPASE scores, the overlap was limited. Qualitative analyses showed that ordinary experiences, medication-related sensations, or psychotic phenomena often were the basis for agreement with IPASE items. CONCLUSIONS: Our findings suggest that, although related, IPASE and EASE do not measure the same construct. The moderate correlation and qualitative discrepancies cast serious doubts on the alledged validity of IPASE for assessing self-disorders, underscoring the importance of phenomenological-clinical interviewing for assessing such psychopathological phenomena.