Longitudinal changes in intolerance of uncertainty and worry severity during CBT for generalized anxiety disorder.

Intolerance of uncertainty (IU) is a key construct in generalized anxiety disorder (GAD), but little is known about the concurrent and temporal patterns of associations between IU and GAD symptom severity during treatment. In addition, most of the extant literature focuses on IU as a unidimensional construct, whereas some researchers conceptualize IU as being comprised of two dimensions, inhibitory and prospective IU. Ninety individuals with GAD completed measures of IU and worry severity at pre-treatment, session 4, session 8, and end of treatment (session 12), during group-based cognitive behavior therapy (CBT) for GAD. Longitudinal multilevel modeling showed that IU predicted worry severity concurrently, but not prospectively over time; this pattern of associations was found with the total IUS score and the inhibitory (but not prospective) subscale score. Further, the relationship between IU total scores and worry severity became stronger over time. The relationship between inhibitory (but not prospective) IU and worry also became stronger over time. When the order of the variables in the model was reversed, worry severity also predicted concurrent but not future IU. Therefore, change in IU is associated with change in worry throughout the course of CBT, particularly as treatment progresses, though its directional association as a cause and/or effect remains unclear.