Generalized anxiety disorder (GAD) is characterized by excessive and uncontrollable worry and anxiety. This common and debilitating anxiety disorder is associated with significant distress as well as substantial impairment in occupational, social, and daily functioning. As a result, effective treatment for GAD is essential. Several cognitive-behavioural treatment (CBT) protocols have been developed for GAD, including an efficacious treatment developed by our research group. This CBT protocol for GAD centres upon intolerance of uncertainty, a dispositional characteristic that arises from a set of negative beliefs about uncertainty and its consequences (Dugas \& Robichaud, 2007). Previous research has shown that individuals with GAD demonstrate high intolerance of uncertainty, and that there are a number of potential pathways by which intolerance of uncertainty may lead to symptoms of GAD (see Dugas \& Robichaud, 2007 for a review). Our CBT protocol targeting intolerance of uncertainty has demonstrated good efficacy across four published randomized clinical trials: approximately 70% of participants have fully remitted from GAD following treatment and have maintained these gains over extended follow-up periods. These results, while positive, do suggest that a substantial minority of individuals do not fully benefit from the existing treatment protocol. Across our randomized clinical trials, individuals who do not achieve diagnostic remission of GAD continue to endorse elevated levels of intolerance of uncertainty. This suggests that the current CBT protocol does not effectively reduce intolerance of uncertainty in some treated individuals. Additionally, the existing treatment protocol has 6 major components, utilizes a number of cognitive and behavioural techniques (including symptom monitoring, motivational interviewing, situational exposure, problem-solving training, and imaginal exposure), and requires at least 14 sessions to implement. Recent literature (e.g., Cougle et al., 2011) has suggested that there is increased need for parsimony and efficiency in CBT protocols. As a result, our research group is investigating new methods of targeting intolerance of uncertainty that demonstrate greater parsimony and efficiency.

Our previous CBT protocol for GAD targeted intolerance of uncertainty directly through situational exposure, and indirectly through motivational interviewing, problem-solving training, and imaginal exposure. In an effort to streamline and strengthen GAD treatment, the newly developed CBT protocol only targets intolerance of uncertainty directly. In this new CBT protocol, intolerance of uncertainty was targeted using behavioural experiments in which participants identified and tested out their beliefs about uncertainty. The extant literature suggests that behavioural experiments are an efficacious way to target the emotional, cognitive, and behavioural components of anxiety disorders and may be superior to habituation-based exposure paradigms (McMillan \& Lee, 2010; Salkovskis et al., 2007).

The current study examined if a newly developed CBT protocol with fewer components could deliver comparable GAD symptom reduction. Seven (7) individuals with a primary diagnosis of GAD completed 12 sessions of CBT using a newly developed treatment protocol focusing exclusively on intolerance of uncertainty. The treatment consisted of 50-minute, weekly sessions targeting intolerance of uncertainty primarily via behavioural experiments. The three treatment components included: (1) psychoeducation and uncertainty awareness training; (2) testing beliefs about uncertainty (via behavioural experiments); and (3) relapse prevention. Measures of GAD symptoms, general psychopathology, and intolerance of uncertainty were administered at pre-, mid-, and post-treatment, as well as at 3- and 6-month follow-ups. Our main outcomes of interest were effect sizes (i.e., relative magnitude of change from pre-posttreatment, pretreatment to 6-month follow-up, and posttreatment to 6-month follow-up).