Increasingly certain about uncertainty: Intolerance of uncertainty across anxiety and depression.

Intolerance of uncertainty (IU) - a dispositional characteristic resulting from negative beliefs about uncertainty and its implications - may be an important construct in anxiety disorders and depression. Despite the potential importance of IU, clinical data on the construct remains relatively scant and focused on generalized anxiety disorder and obsessive-compulsive disorder. The present study systematically investigated IU, as measured by the Intolerance of Uncertainty Scale-12 (IUS-12), across groups diagnosed with anxiety disorders (i.e., social anxiety disorder, panic disorder, generalized anxiety disorder, obsessive-compulsive disorder) or depression (clinical sample: n=376; 61% women), as well as undergraduate (n=428; 76% women) and community samples (n=571; 67% women). Analysis of variance revealed only one statistically significant difference in IUS-12 scores across diagnostic groups in the clinical sample; specifically, people with social anxiety disorder reported higher scores (p<.01; η(2)=.03) than people with panic disorder. People diagnosed with an anxiety disorder or depression reported significantly and substantially higher IUS-12 scores relative to community and undergraduate samples. Furthermore, IUS-12 score distributions were similar across diagnostic groups as demonstrated by Kernel density estimations, with the exception of panic disorder, which may have a relatively flat distribution of IU. Response patterns were invariant across diagnostic groups as demonstrated by multi-group confirmatory factor analyses, but varied between clinical and nonclinical samples. Overall, the findings suggest IU may serve as an important transdiagnostic feature across anxiety disorders and depression. In addition, robust support was found for the proposed 2-factor model of the IUS-12. Comprehensive findings, implications, and future research directions are discussed.