A Randomized Clinical Trial Comparing an Acceptance-Based Behavior Therapy to Applied Relaxation for Generalized Anxiety Disorder

Objective: To examine whether an empirically and theoretically derived treatment combining mindfulness- and acceptance-based strategies with behavioral approaches would improve outcomes in generalized anxiety disorder (GAD) over an empirically supported treatment. Method: This trial randomized 81 individuals (65.4% female, 80.2% identified as White, average age 32.92) diagnosed with GAD to receive 16 sessions of either an acceptance-based behavior therapy (ABBT) or applied relaxation (AR). Assessments at pretreatment, posttreatment, and 6-month follow-up included the following primary outcome measures: GAD clinician severity rating, Structured Interview Guide for the Hamilton Anxiety Rating Scale, Penn State Worry Questionnaire, Depression Anxiety Stress Scale, and the State-Trait Anxiety Inventory. Secondary outcomes included the Beck Depression Inventory-II, Quality of Life Inventory, and number of comorbid diagnoses. Results: Mixed effect regression models showed significant, large effects for time for all primary outcome measures (ds = 1.27 to 1.61) but nonsignificant, small effects for condition and Condition x Time (ds = 0.002 to 0.20), indicating that clients in the 2 treatments improved comparably over treatment. For secondary outcomes, time was significant (ds = 0.74 to 1.38), but condition and Condition x Time effects were not (ds = 0.004 to 0.31). No significant differences emerged over follow-up (ds = 0.03 to 0.39), indicating maintenance of gains. Between 63.3 and 80.0% of clients in ABBT and 60.6 and 78.8% of clients in AR experienced clinically significant change across 5 calculations of change at posttreatment and follow-up. Conclusion: ABBT is a viable alternative for treating GAD.