Peter's delusions inventory in Spanish general population: internal reliability, factor structure and association with demographic variables (dimensionality of delusional ideation).

INTRODUCTION: Several lines of evidence suggest the existence of a continuum on psychotic symptoms, including delusions. Moreover, several studies have reported differences regarding prevalence and intensity of these symptoms in relation to age, gender and educational level. This study tries to analyze distribution and dimensionality of delusional ideation in the general population, as well as relationship between gender, age and educational level with the prevalence of these symptoms.

METHOD: We used the 21-item Peters. Delusions Inventory (PDI-21) on a general population sample as our measure of delusional ideation. A factor analysis was carried out to determine the dimensionality of delusional ideation. Next, linear regression analyses were performed to analyze the relationship of age, gender and educational level with the different dimensions.

RESULTS: 365 subjects completed the inventory. Factor analysis revealed the presence of 7 easily interpretable factors. Five of these factors were negatively correlated with age. Women had higher scores on the "magical thinking" factor. Finally, lower educational level was correlated with higher scores on those factors of "magical thinking" and "experiences of influence".

CONCLUSIONS: It appears that the PDI-21 is a useful instrument to measure dimensionality of delusional ideation in Spanish general population. Results of the influence of gender, age and educational level are in agreement with those reported in psychosis samples, supporting the existence of a continuum in psychoses.