Hierarchical factor structure of the Intolerance of Uncertainty Scale short form (IUS-12) in the Italian version

Despite widespread use, few translations are available for the Intolerance of Uncertainty Scale short form (IUS-12) as well as limited research on its psychometric properties in Italy. Moreover, recent evidence has suggested a multifaceted hierarchical structure for this scale. We compared the two-factor model to second-order and bi-factor models, in which a General IU factor was posited with two more narrow factors: Prospective IU and Inhibitory IU. Models were tested on a pooled dataset of students (N = 609) taking the IUS-12 alone or with other IUS-27 items. The bi-factor model fitted the sample data better than alternative models. The general factor accounted for 80% of the item variance. Presentation mode did not impact scalar invariance. Convergent validity with neuroticism, need for closure, and the uncertainty response scale was high for the total score. As such, scoring the IUS-12 total score is recommended in clinical research and assessment