How Is “Intolerance of Uncertainty” (IU) Measured? A Systematic Review of Assessment Tools for IU and the Psychometric Properties of IU Questionnaires

Objective: Intolerance of uncertainty (IU), a negative cognitive, emotional, and behavioral response to uncertainties, is a transdiagnostic trait associated with a wide range of mental health conditions. To clarify which IU assessment tools are best used in clinical or nonclinical populations, the present study aimed to systematically identify all IU measures and synthesis the psychometric properties of IU questionnaires. Method: Six databases including PubMed, Medline, Embase, PsycInfo, Web of Science, and Scopus were searched in two stages. All the evidence of psychometric properties were extracted, assessed, and summarized following the adapted COnsensus-based Standards for the selection of health Measurement INstruments guidelines by two independent reviewers. Results: Forty-seven questionnaire names relevant to the concepts of IU or uncertainty were identified in Stage 1. Fifty-four IU-relevant articles and seven IU questionnaires were identified in Stage 2. There was no best measure for IU that reported the best psychometric properties with the best quality measure. Most of the IU questionnaires only reported sufficient internal consistency and convergent validity with good quality. Discussion: Recommendations for the choice of IU questionnaire to be used in the general population, specific populations, different age groups, and assessing distinct aspects of IU are given. Future research could develop or adapt IU measures to address the issues around the psychometric properties raised in this study. Intolerance of uncertainty (IU)—extremely negative response to uncertainties—is a trait associated with poor mental health. Measuring IU accurately is vital for understanding a wide range of mental health conditions and for interventions. In this study, we identified all IU assessment tools and evaluated the psychometric properties of IU questionnaires (the most commonly used type of IU measure). Suggestions are given for clinicians and researchers to help them select the most suitable IU questionnaire for specific purposes, situations, and target populations.