Intolerance of uncertainty as a mediator of reductions in worry in a cognitive behavioral treatment program for generalized anxiety disorder

Highlights

• Intolerance of uncertainty (IU) is theorized to be a key factor pathological worry.

• The effect of CBT on IU and worry was examined over the course of CBT.

• Changes in IU mediated subsequent changes in worry.

Abstract

Growing evidence suggests that intolerance of uncertainty (IU) is a cognitive vulnerability that is a central feature across diverse anxiety disorders, including generalized anxiety disorder (GAD). Although cognitive behavioral therapy (CBT) has been shown to reduce IU, it remains to be established whether or not reductions in IU mediate reductions in worry. This study examined the process of change in IU and worry in a sample of 28 individuals with GAD who completed CBT. Changes in IU and worry, assessed bi-weekly during treatment, were analyzed using multilevel mediation models. Results revealed that change in IU mediated change in worry (ab = −0.20; 95% CI [−.35, −.09]), but change in worry did not mediate change in IU (ab = −0.16; 95% CI [−.06, .12]). Findings indicated that reductions in IU accounted for 59% of the reductions in worry observed over the course of treatment, suggesting that changes in IU are not simply concomitants of changes in worry. Findings support the idea that IU is a critical construct underlying GAD.

Introduction

Intolerance of uncertainty (IU), the dispositional tendency to experience fear of the unknown, is considered to be an important factor in the development and maintenance of anxiety disorders (Carleton, 2012). IU includes beliefs that uncertainty is threatening, stressful, and anxiety provoking, as well as the desire to avoid situations where uncertainty and ambiguity may be present (Buhr and Dugas, 2002, Dugas et al., 2001). Although IU likely contributes to multiple anxiety disorders (e.g., Carleton, 2012), the most comprehensive conceptual model of the relationships between IU and anxiety psychopathology was designed primarily to account for symptoms of generalized anxiety disorder (GAD; Dugas, Gagnon, Ladouceur, & Freeston, 1998). GAD features worry, defined as “repetitive, uncontrollable thoughts about negative life events” (Segerstrom, Tsao, Alden, & Craske, 2000), as a predominant symptom (American Psychiatric Association, 2013). For those high in IU, the possibility of negative outcomes is proposed to trigger maladaptive behavioral and cognitive reactivity (e.g., biased interpretations of the situation, increased need for information during decision-making) that serve to increase worry and anxiety (Dugas et al., 2005, Dugas and Robichaud, 2007, Ladouceur et al., 2000). Moreover, IU contributes to other problematic cognitive processes, including poor problem orientation and cognitive avoidance, which conjointly and paradoxically maintain worry and anxiety (Dugas & Robichaud, 2007).

Data from several treatment outcome studies indicate that anxiety interventions impact IU, and suggest that IU may play a role in maintaining anxiety. Dugas and colleagues (e.g., Dugas et al., 2003, Dugas et al., 2010, Dugas and Ladouceur, 2000) have developed a cognitive-behavioral intervention specifically to address IU as part of a comprehensive treatment for GAD, which has been shown to effectively decrease IU and other symptoms (e.g., worry, depression). Other types of CBT interventions that do not feature an explicit focus on IU also appear to reduce IU in GAD (e.g., Boswell et al., 2013, Hewitt et al., 2009, van der Heiden et al., 2012). Thus, preliminary evidence suggests that IU is malleable with CBT interventions in individuals with GAD. Establishing IU as a process relevant to symptom reduction is critical to validate cognitive theories and to identify treatment strategies to optimize therapeutic outcomes (Kazdin, 2007, Smits et al., 2012). The aforementioned treatment outcome studies provide evidence that IU changes from pre to post treatment, but the process by which IU changes relative to other symptoms has not been empirically established. For example, it is possible that reducing IU lessens worry, or that IU levels are lower at the end of treatment because worry or general anxiety symptoms have decreased. One case-controlled study suggests that reductions in IU precede reductions in worry in treatment for GAD (Dugas & Ladouceur, 2000). An analogue study of exposure-based treatment components also suggested that reductions in IU predicted subsequent reductions in worry (Goldman, Dugas, Sexton, & Gervais, 2007). Further support for a causal relationship between IU and worry comes from experimental psychopathology studies indicating that manipulating IU appears to impact worry (Ladouceur et al., 2000, Meeten et al., 2012). However, models suggesting reduction in IU as a mediator of reductions in worry longitudinally over the course of treatment have yet to be confirmed empirically. Evaluating whether or not changes in IU precede and account for symptom change during treatment provides a more rigorous test of the hypothesis that IU is a core construct that perpetuates worry and anxiety (Kazdin, 2007).

The present study examined the process of change in IU and worry in a sample of individuals with GAD who completed a CBT program. The goal of the analyses was to test the proposed mediational relationship outlined in models of GAD and worry—specifically that reductions in IU would account for reductions in worry over the course of treatment. Using data from an open trial of a transdiagnostic CBT treatment protocol for anxiety, changes in IU and worry assessed at pre-treatment and bi-weekly during treatment were analyzed using multilevel mediation procedures. We hypothesized that reductions in IU would mediate subsequent reductions in worry across sessions.