Abstract

Generalized anxiety disorder (GAD) is characterized by excessive worry and somatic symptoms of anxiety (e.g., restlessness, muscle tension) ( DSM-IV-TR , 2000). Although efficacious treatments have been developed, little is known about the nature and predictors of symptom change during treatment. Dugas and colleagues have developed a cognitive-behavioural therapy (CBT) for GAD which has been found to be efficacious in reducing worry and somatic anxiety in pre-to-posttreatment analyses (e.g., Dugas et al., 2010). This CBT is based on a cognitive model (Dugas et al., 1998) which implicates intolerance of uncertainty in the development and maintenance of GAD. The first goal of this study was to examine the nature of GAD symptom change during CBT. The second goal was to examine the role of intolerance of uncertainty, and its two component factors, in GAD symptom change. The results indicated that there was a bidirectional relationship between changes in worry and changes in somatic anxiety during treatment. In addition, intolerance of uncertainty was found to partially mediate GAD symptom change over time. However, different mediational roles were identified for the two factors, which represent distinct sets of beliefs about uncertainty. Specifically, Factor 2 (i.e., Uncertainty is unfair and spoils everything), was a stronger mediator of GAD symptom change than Factor 1 (i.e., Uncertainty has negative self-referential and behavioural implications). The theoretical and clinical implications of these findings are discussed.