Development of the Delusional Interpretation Scale and examination of related variables.

Aim: Delusions are a common symptom in schizophrenia. Some scales have been developed to measure delusional tendencies in healthy people, and nonpathological delusional thinking can occur even among these individuals. The existing scales measure the presence and frequency of delusional thoughts, distress levels, and confidence levels. However, these scales are limited because they do not consider the context of the delusions (i.e., where, with whom, and when). In this study, we developed a new scale that presents detailed scenes using illustrations and sentences and measures the tendency toward delusional interpretations.

Methods: Factor analysis was conducted to confirm the factor structure of the new scale. To examine the validity of the scale, we analyzed the correlations between delusional tendencies and related variables and verified the consistency between the current scale and previously developed tools.

Results: Factor analysis confirmed that the new scale has a two-factor structure, including "internal attribution and paranoid tendency" and "external attribution tendency." The new scale was found to have acceptable reliability and validity. The internal attribution and paranoid tendency factor was negatively correlated with self-esteem and decentering. Furthermore, the internal attribution and paranoid tendency factor showed a moderate positive correlation with depressive state and anxiety tendency and a very weak positive correlation with experiences of bullying or harassment.

Conclusion: The correlations between the new scale and related variables confirmed the construct validity and replicated the results reported in previous studies. This new scale enables the measurement of delusional tendencies in healthy subjects based on the social context.