Psychometric validation of the obsessive belief questionnaire and interpretation of intrusions inventory--Part 2: Factor analyses and testing of a brief version

The Obsessive Belief Questionnaire (OBQ) and the Interpretation of Intrusions Inventory (III) were designed to assess beliefs and appraisals considered critical to the pathogenesis of obsessions. In previous reports we have described the construction and psychometric properties of these measures. In this study a battery of questionnaires assessing anxiety, depression, and obsessive compulsive symptoms was completed by 410 outpatients diagnosed with obsessive compulsive disorder, 105 non-obsessional anxious patients, 87 non-clinical adults from the community, and 291 undergraduate students. Items from 6 theoretically derived subscales of the OBQ were submitted to factor analysis. Three factors emerged reflecting (1) Responsibility and threat estimation, (2) Perfectionism and intolerance for uncertainty, and (3) Importance and control of thoughts. A 44-item version (OBQ-44) composed of high-loading items from the 3 factors showed good internal consistency and criterion-related validity in clinical and non-clinical samples. Subscales showed less overlap than original scales. Factor analysis of the III yielded a single factor, suggesting the total score be used in lieu of the 3 rationally derived subscales. The scales performed well on tests of convergent validity. Discriminant validity was promising; hierarchical regression analyses indicated that the OBQ subscales and III generally predicted OC symptoms after controlling for general distress. A revision of the OBQ, the OBQ-44, is included in the appendix.