Psychometric properties of Peters et al. Delusions Inventory-21 in adolescence

We explored the psychometric properties of the Korean version of the Peters et al. Delusions Inventory-21 (PDI-21) and evaluated the item characteristics of the PDI-21 compared with the Magical Ideation Scale (MIS) in Korean community adolescents. Survey participants comprised 310 Year 10 students who were assessed with the following instruments: the PDI-21, the MIS, the Schizotypal Personality Scale (STA) and the Symptom Checklist-90-R (SCL-90-R). The item characteristics of the PDI-21 and MIS were also explored using item response theory (IRT). The PDI-21 exhibited good internal consistency and demonstrated significant correlations with the MIS, STA and all subscale scores of the SCL-90-R, indicating psychological distress in adolescents with high PDI-21 scores. We also found through IRT analysis that the PDI-21 provides more information at the lower range and the MIS at the higher range of delusion proneness. Our findings suggest that the PDI-21 is an effective and reliable self-report measure for assessment of delusion proneness and that the PDI-21 and the MIS may be used complementarily to assess a broad range of delusion proneness among community adolescents.