Time-varying moderation of treatment outcomes by illness duration and comorbid depression in generalized anxiety disorder.

OBJECTIVE: To extend the sparse literature on moderators, we used time-varying effect modeling (TVEM; Tan, Shiyko, Li, Li, & Dierker, 2012) to examine how depressive symptoms and duration of generalized anxiety disorder (GAD) moderated effects of 3 treatments for GAD (applied relaxation [AR], cognitive-behavioral therapy [CBT], and nondirective therapy [ND]) over time using intensive repeated measures.

METHOD: In a secondary analysis of Borkovec and Costello (1993), 66 GAD clients were randomly assigned to AR (n = 23), CBT (n = 23), or ND (n = 20). Clients received 12 therapy sessions over 6 weeks, and after 2 weeks of posttreatment assessment, had 2 additional weekly fading sessions. They completed thrice daily anxiety ratings during this 10-week period. GAD duration (Anxiety Disorders Interview Schedule-Revised) and depressive symptoms (Hamilton Depression Rating Scale) were assessed at baseline.

RESULTS: Longer GAD duration predicted less anxiety reduction in CBT and ND relative to AR. These effects were pronounced in the later phase of treatment, suggesting benefits of focused relaxation practice for clients with longer duration. Higher depression predicted better response to CBT than AR and ND. The moderation effects were also more noticeable in the later phase. In multilevel analyses, a similar moderation pattern held at 1-year follow-up on clinician-rated measures.

CONCLUSION: GAD clients with long-standing symptoms may benefit more from repeatedly practicing fewer skills than learning multiple skills. On the other hand, clients with comorbid depression may respond better to CBT than AR, perhaps because CBT includes cognitive interventions that can generalize to depression. (PsycINFO Database Record (c) 2019 APA, all rights reserved).