The Polish version of the Peters et al. Delusions Inventory: factor analysis, reliability and the prevalence of delusion-like experiences in the Polish population.

AIM: The study aimed at providing the psychometric properties of Polish version of Peters et al. Delusion Inventory (PPDI) (1999) and assessing the prevalence of delusion-like experiences among healthy subjects in the Polish population.
METHODS: Polish version of PDI was developed on the basis of back translation procedure. The scale was completed by 421 adult subjects. On the basis of the scores, the factor analysis, the reliability of the scale and the frequency of delusion-like experiences in the Polish population were calculated.
RESULTS: The Polish version of Peters et al. Delusion Inventory has satisfactory reliability (Cronbach's alpha ranged from 0.084 to 0.87). The examination of scree plot suggests a single factor solution. The participants confirmed the incidence of, on average, 12.5 (SD=6.9), out of 40 different experiences measured using PDI. In the current study the most frequently asserted delusion-like belief is that people say things with double meaning (79.8% of participants), while the least likely beliefs were those similar to delusions observed among psychiatric patients (2.37% of participants).
CONCLUSIONS: The Polish version of PDI is characterised by good psychometric properties and can be used for delusion-like experiences assessment in non-clinical population. The frequency of delusion-like experiences in the Polish population varies from 2 to 80% depending on their content.