Construction of scales to measure thematic tendencies of paranoid ideation

In order to measure thematic tendencies of paranoid ideation in non-clinical samples, Delusional Ideation Checklist (DICL) was developed. A wide range of items indicating themes of delusion were collected. From the results of factor analysis on the data of 308 college students, eight scales were constructed. They were: alienation, belittlement, persecution, other-harming, guardedness, self-conceit, favoredness, and other-manipulation. These scales could be classified in terms of emotion: positive versus negative, and direction: self versus others, and could deal with themes of paranoid ideation in a comprehensive and systematic way. Alpha coefficients of the scales were between .66 and .87, and test-retest reliability between .49 and .71. To examine content validity, ten psychiatrists were asked to rate diagnostic importance for each scale item. Six scales were rated as significantly more important in the diagnosis of paranoid schizophrenia than that of anxiety neurosis. Current data revealed that ordinary students experienced delusional ideation more frequently than psychiatrists would expect.