Validation of the Arabic 21-Item Peters et al. Delusions Inventory (PDI-21): Prevalence, Factor Structure,...

Making available a sound tool to screen for delusion experiences at a nonclinical level in Arabic-speaking contexts could enable the timely detection of at-risk individuals, advance understanding of the phenotypic expression of delusions and provide new insights into the relationship of delusion experiences with different psychopathological indicators at a subclinical level. The purpose of this study was to validate the 21-item Peters et al. Delusions Inventory (PDI-21) in the Arabic language.

A cross-sectional study was conducted during the period from August 2025 to January 2026. The sample consisted of 706 community adults aged 18-35 years. To obtain the Arabic version of the PDI-21, the scale underwent a rigorous translation process using the standard Backward-Forward method and following the international guidelines. Confirmatory factor analysis was conducted to examine the factor structure of the scale. Reliability, convergent validity and measurement invariance across gender were also assessed.

The prevalence rates of self-reported delusion experiences in our sample ranged from 10% to 79%. Seven items showed an endorsement rate above 40%. The single-dimension structure had an overall acceptable fit with the data, with strong support from the CFI, TLI and RMSEA despite a slightly elevated SRMR and moderate average variance extracted (AVE) values. Loadings on the one factor ranged from 0.37 to 0.78. The total score exhibited excellent internal consistency reliability, as reflected by a Cronbach's alpha of 0.82. Measurement invariance was established across sex. Convergent validity was achieved by observing a moderate-to-strong positive correlation between PDI-21 scores and psychotic experiences frequency score. In addition, concurrent validity was supported by showing that individuals who endorsed greater delusion experiences had higher psychological distress, greater stress levels and more childhood trauma.

This study provided evidence for satisfactory reliability and validity for the single-dimension PDI-21 in its Arabic version. The scale can now be used by professionals working with Tunisian and other Arabic-speaking populations as a robust and accurate tool for assessing delusional beliefs among community adults, with future cross-national studies being needed to further establish its generalizability across diverse Arabic-speaking contexts.