Seeking certainty about Intolerance of Uncertainty: Addressing old and new issues through the Intolerance of Uncertainty Scale-Revised

Intolerance of Uncertainty is a trans-diagnostic process that spans a range of emotional disorders and it is usually measured through the Intolerance of Uncertainty Scale-12. The current study aims at investigating some issues in the assessment of Intolerance of Uncertainty (IU) through the Italian Intolerance of Uncertainty Scale-Revised, a measure adapted from the Intolerance of Uncertainty Scale-12 to assess IU across the lifespan. In particular we address the factor structure among a large community sample, measurement invariance across gender, age, and over time, together with reliability and validity of the overall scale and its subscales. The questionnaire was administered to community (N = 761; mean age = 35.86 +/- 14.01 years) and undergraduate (N = 163; mean age = 21.16 +/- 2.64 years) participants, together with other self-report measures assessing constructs theoretically related to IU. The application of a bifactor model shows that the Italian Intolerance of Uncertainty Scale-Revised possesses a robust general factor, thus supporting the use of the unit-weighted total score of the questionnaire as a measure of the construct. Furthermore, measurement invariance across gender, age, and over time is supported. Finally, the Italian Intolerance of Uncertainty Scale-Revised appears to possess adequate reliability and validity. These findings support the unidimensionality of the measure, a conceptually reasonable result in line with the trans-diagnostic nature of Intolerance of Uncertainty. In addition, this study and comparison with published factor structures of the Intolerance of Uncertainty Scale-12 and of the Intolerance of Uncertainty Scale-Revised identify some issues for the internal structure of the measure. In particular, concern is expressed for the Prospective IU subscale. In light of the promising psychometric properties, the use of the Italian Intolerance of Uncertainty Scale-Revised as a univocal measure is encouraged in both research and clinical practice.