The IUS-4: A Psychometric Evaluation of an Ultra-Brief Intolerance of Uncertainty Measure

Abstract This study investigated the psychometric properties of a newly proposed ultra-brief version of the Intolerance of Uncertainty Scale (IUS), the IUS-4. Intolerance of uncertainty, a broad cognitive, emotional, and behavioral reaction to ambiguous or uncertain situations, is a transdiagnostic variable associated with various psychopathologies, including anxiety and depression. While the 27-item IUS and its 12-item short form (IUS-12) are widely used, shorter versions are needed for efficiency in clinical and research settings. The IUS-4 comprises four items from the IUS-12 designed to capture the core construct of intolerance of uncertainty. This study aimed to: (a) develop an ultra-brief version of the IUS and examine its factor structure, (b) estimate its reliability, (c) analyze measurement invariance across sexes, and (d) establish its relationship with anxiety, depression, emotional dysregulation, and worry. A sample of 1,374 participants who sought psychological help completed an online questionnaire. Confirmatory factor analysis supported a unidimensional model for the IUS-4, with acceptable internal consistency (omega = 0.81). Multigroup invariance analysis confirmed equivalence across sexes. Associative validity was demonstrated through positive correlations between the IUS-4 and measures of emotional dysregulation, depression, worry, and, to a lesser extent, anxiety. These findings suggest that the IUS-4 is a reliable and valid measure of intolerance of uncertainty, offering a practical and efficient tool for assessment in research and clinical practice.