Still fearing the unknown: Development and initial validation of an ultra-brief intolerance of uncertainty scale

The 12-item Intolerance of Uncertainty Scale (IUS-12) is a widely used measure in anxiety disorders research and clinical practice, although recent research efforts have recommended the development of a briefer measure to reduce response burdens. The current study was designed to develop a short form of the IUS-12. We administered the IUS-12 to two samples (cross-sectional, n = 3952; longitudinal, n = 190) of Canadian Public Safety Personnel through an online self-report survey. Exploratory (EFA) and confirmatory (CFA) factor analyses assessed the factor structure of the IUS-12 and facilitated item reduction and optimization. Convergent and concurrent validity, as well as pre-post rank-order consistency were also assessed. The IUS-12 was reduced to a two-factor, six-item short form (i.e., IUS-6) that retains the factor structure of the IUS-12 with statistically comparable validity and consistency, which appears to retain the intended latent content for each subscale. Very strong statistically significant positive correlations were observed between IUS-6 and IUS-12 subscales (rs = .90-.94) and total scores (r = .95) for all samples, suggesting excellent construct validity. Moderate to strong statistically significant associations were also observed among the IUS-6 and IUS-12 total and subscales and measures of generalized anxiety, social anxiety, and anxiety sensitivity, suggesting good convergent validity (rs = .23-.64), with only small differences in correlation strengths (i.e., r < .14). The IUS-6 may be used as an ultra-short version of the IUS-12 for assessing self-reported intolerance of uncertainty in both cross-sectional and longitudinal research designs, potentiating reduced response burdens, which may be important in various research and clinical settings.