Psychometric properties of the Questionnaire for Psychotic Experiences (QPE) in an Italian general population sample

Introduction: Psychotic experiences, such as hallucinations and delusions, are present in various psychiatric disorders, including schizophrenia, bipolar disorder, and major depressive disorder. They have also been reported in individuals in the general population, although typically in milder and less disabling forms. To enable a comprehensive understanding and transdiagnostic comparison of the wide range of these phenomena, a new measure, the Questionnaire for Psychotic Experiences (QPE), was developed. The QPE assesses hallucinations and delusions from a qualitative and quantitative perspective. The aim of this study was to validate the Italian version of the QPE and to examine its psychometric properties. Method: A total of 87 participants (mean age = 29.3 ± 7.4 years; 62.1% female) completed the Italian version of the QPE, which had been previously translated and cross-culturally adapted. Additionally, they completed three self-report instruments: a) CAPE, which measures psychotic experiences and related distress; b) STAY, which assesses current anxiety state and a general tendency to be anxious; and c) SCL-90-R, which measures a broad range of psychopathological symptoms. Cronbach’s alpha and Kendall’s tau correlation coefficients were used to assess the reliability and validity of the QPE. Results: The QPE subscales demonstrated good internal consistency, with Cronbach’s alpha ranging from .70 to .85. They also showed positive and significant correlations with the conceptually related CAPE and its subscales, particularly the one measuring positive symptoms, providing evidence for convergent validity. Conversely, weak or null correlations with the conceptually unrelated STAY and its subscales support the QPE’s divergent validity. Discussion: The QPE is a reliable and valid tool for assessing a wide range of psychotic experiences across diagnoses. Further research is needed to explore differences in psychotic experiences between clinical and nonclinical populations.