Date of Award


Document Type

Campus Access Thesis

Degree Name

Master of Arts (MA)


Clinical Psychology

First Advisor

Sarah Hayes-Skelton

Second Advisor

Lizabeth Roemer

Third Advisor

Abbey Eisenhower


The goal of the present study was to find the best-fitting models for mindfulness, acceptance, and valued action trajectories across acceptance-based behavioral therapy (ABBT) for generalized anxiety disorder (GAD), compare their associations, and determine their individual and combined effect on reduction of GAD symptoms. Better understanding the processes of change in treatment components could inform clinicians about clinical adjustments needed for certain individuals and begin to answer questions about the importance of each component in predicting outcomes. The current study is the first to compare trajectories of change within ABBT. We examined weekly assessment data from the ABBT arm of a randomized control trial comparing the efficacy of a 16-session ABBT to applied relaxation therapy for individuals with a principal diagnosis of GAD (Hayes-Skelton, Roemer, & Orsillo, 2013). Participants answered questions about three components of ABBT, including the percentages of time spent over their past week being aware of the present moment (mindfulness), accepting of their internal experiences (acceptance), and engaging in valued action (valued action), as well as a self-report measure of GAD symptoms (DASS-21 Stress subscale) at pre- and post-treatment. The sample consisted of 31 (mean age = 34.97) predominantly white individuals. Findings showed that acceptance and valued action components of ABBT increased linearly, whereas the mindfulness component indicated a slight curve in its trajectory. Trajectories of mindfulness, acceptance, and valued action were all significantly, positively correlated with one another (ps < .001). In this sample, neither early changes in mindfulness nor early changes in acceptance predicted later changes in valued action. When examining the linear models of each component separately, we found that increases in acceptance (p < .001) and valued action (p = .05) significantly predicted decreases in GAD symptoms. A regression showed that improvements in all three components had a significant effect on GAD outcome above and beyond the effect indicated by participants’ baseline levels of mindfulness, acceptance, and valued action. The regression also revealed that the intercept of valued action (p = .02) and the linear slope of acceptance (p = .03) were driving improvements in GAD symptoms, with both the intercept (p = .07) and slope (p = .10) of mindfulness trending towards significance. Altogether, these results suggest that, on average, individuals with GAD make incremental changes in the three ABBT components across 16 sessions of treatment and that increases in each component help individuals make improvements in another. These findings are consistent with the structure of treatment and support an acceptance-based treatment model. Further research is needed to explore the trajectories of ABBT components and their effect on treatment outcome.


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