Date of Award




Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Psychology


Clinical Psychology

Content Description

1 online resource (x, 186 pages) : illustrations.

Dissertation/Thesis Chair

John P Forsyth

Committee Members

Drew A Anderson, Georg H Eifert


Acceptance and Commitment Therapy, Anxiety, Meditation, Mindfulness, Values, Values Clarification, Mindfulness-based cognitive therapy, Values clarification

Subject Categories

Clinical Psychology | Psychiatric and Mental Health | Psychology


Anxiety disorders are the most prevalent mental health concern in the United States. Yet, many who suffer from anxiety do not receive treatment or fail to respond to well-established cognitive and behavioral interventions. Mindfulness- and values-based strategies are possible alternatives for these individuals. However, values-based approaches have not been adequately studied in anxious populations and it is unclear how they may interact with mindfulness-based approaches. Moreover, little is understood about the mechanisms of action underlying behavioral changes resulting from mindfulness meditation (MM) practices. Acceptance and Commitment Therapy (ACT) is one approach that employs values clarification (VC) and mindfulness to bring about improvements in quality of life (QOL). ACT also provides a behavioral account of human vitality that may increase specificity of mediating and moderating variables that are critical for good outcomes following mindfulness-based treatment. The present investigation aimed to evaluate the effects of MM and VC on QOL and anxiety symptomology and to elucidate significant mediators and moderators of the relations between MM and VC and positive outcomes. In so doing, highly anxious participants (N = 120) were randomly assigned to a 10-min MM practice + control task or a 10-min MM practice + VC task. Pre, post, and daily diary assessments were employed over the course of 16 days and included several well-established process and outcome measures. Results suggest that 2-weeks of MM practice leads to decreases in anxiety symptom frequency and increases in QOL during the previous 24-hour cycle. VC did not significantly affect primary outcomes. Acceptance appears to be the most important mediator assessed herein of the daily effects of mindfulness on anxiety symptoms, though valued action was a numerically stronger mediator between mindfulness and QOL. Practice quality was related to daily reductions in anxiety symptoms and improvement in daily QOL. However, it did not moderate response to MM. Surprisingly, MM practice time, when controlling for average practice quality, was related to worse QOL outcomes for those who participated in VC. Results are discussed in terms of enhancing the impact of psychological treatments for the anxiety disorders, in addition to implications for personal mindfulness meditation practices.