The inventory of psychotic-like anomalous self-experiences (IPASE): Stability and relationships with attenuated psychotic symptoms and remission in individuals at-risk for psychosis

Background: The IPASE is a self-report measure of basic self-disturbance, a core feature of schizophrenia and ultra-high risk (UHR) states. However, the extent to which basic self-disturbance—as captured by the IPASE—is stable over time and related to the severity or progression of attenuated psychotic symptoms (APS) remains unclear. We examined the temporal stability of IPASE scores, their correlation with APS, and whether they predict changes in APS over time. Methods: The baseline sample included 185 participants (healthy controls = 72, UHR = 66, first-episode psychosis = 47), with 29 UHR participants re-assessed at month-12. Correlations between IPASE scores and Comprehensive Assessment of At-Risk Mental States (CAARMS) positive symptom scores were evaluated at baseline and month-12. Stability between baseline and month-12 IPASE scores was examined in the longitudinal subsample. Regression was used to predict remission and change in CAARMS scores. Results: Although mean IPASE scores were significantly higher in the UHR group compared to HCs, total IPASE scores were only weakly correlated with CAARMS total scores (ρ=0.27). IPASE subscales showed weak correlations (0.08<ρ<0.27) with CAARMS positive symptom domains. Changes in IPASE and CAARMS scores were not correlated. Moderate stability was found for IPASE total scores (ICC = 0.59) and four subscales (0.58 < ICC < 0.64), excluding the cognition subscale (ICC = 0.3). Baseline IPASE scores did not predict remission (partial R²=0.05) or change in CAARMS scores (partial R²=0.02). Conclusion: The IPASE is a moderately stable measure in UHR individuals, correlates with the presence of positive psychotic symptoms but only weakly with severity, and does not strongly predict positive symptom change.