A short-form version of the Intolerance of Uncertainty Scale: Initial development of the IUS-5

Intolerance of Uncertainty (IU) is an individual´s "tendency to be bothered or upset by the (as yet) unknown elements of a situation, whether the possible outcome is negative or not." This construct, originally proposed in the context of Generalised Anxiety Disorder (GAD), is now considered a transdiagnostic construct. The Intolerance of Uncertainty Scale (IUS; Freeston, Rhéaume, Letarte, Dugas, & Ladouceur, 1994) has been the gold standard measure for IU, both the original 27-item and the 12-item (IUS-12; Carleton, Norton, & Asmundson, 2007) versions. The present study, conducted in the context of a broader research project about IU and the COVID-pandemic by the UNiCORN team, aims to develop an even shorter version of the IUS, both psychometrically sound and quicker to administer, which would increase its utility in research studies with an elevated number of measures. Initial analyses conducted in currently available data from four countries (UK, Italy, Spain and Greece) suggest that it is possible to reduce the IUS-12 to 5 items, including two items measuring desire for predictability, one item assessing uncertainty paralysis, and two items describing aversiveness of uncertainty. The five-item version of the questionnaire (IUS-5) showed adequate internal consistency across languages (English, Italian, Spanish, Greek) and across situations (e.g., before and during COVID-19), and its total score is highly correlated with the total score of the IUS-12. Overall, preliminary results suggest that the IUS-5 may represent a valid and reliable measure of IU to be used across samples, languages, and countries.