Predictors of CBT outcome in older adults with GAD

Highlights

• We examined predictors of outcome in older adults receiving CBT for GAD.

• Lower initial symptom severity predicted better outcome.

• Variables representing engagement in treatment predicted better outcome.

Abstract

The current study is a secondary analysis of data from a randomized controlled trial of CBT for late-life GAD (Stanley et al., 2014) which provided an opportunity to examine predictors of outcome among those who received CBT. Participants were 150 older adults who were randomized to receive 10 sessions of CBT. Completer analyses found that homework completion, number of sessions attended, lower worry severity, lower depression severity, and recruitment site predicted 6-month worry outcome on the PSWQ-A, whereas homework completion, credibility of the therapy, lower anxiety severity, and site predicted 6-month anxiety outcome on the STAI-T. In intent-to-treat multivariate analyses, however, only initial worry and anxiety severity, site, and number of sessions completed predicted treatment outcome. These results are largely consistent with predictors of outcome in younger adults and suggest that lower initial symptom severity and variables consistent with greater engagement in treatment predict outcome.

Introduction

Cognitive behavioral therapy (CBT) for generalized anxiety disorder (GAD), which typically includes relaxation, breathing, sleep hygiene techniques, cognitive restructuring, and problem solving, is effective for adults, with moderate to large effect sizes (Cuijpers et al., 2014, Hanrahan et al., 2013). Older adults with GAD represent an underserved population in that symptoms of anxiety are often unrecognized by providers and patients themselves (APA, 2005) and older adults are less likely to access and utilize psychotherapy (Karel, Gatz, & Smyer, 2012). Unfortunately, even when older adults do seek psychotherapy for GAD, treatment may be less effective than in younger or middle-aged adults (Covin, Ouimet, Seeds, & Dozois, 2008). Nevertheless, CBT for GAD remains the treatment modality with the most research support in older adults (Goncalves and Byrne, 2012, Wolitzky-Taylor et al., 2010).

Understanding factors that predict treatment outcome in psychotherapy may help improve the effectiveness of treatment and tailor treatments to specific patient groups. There is extensive research regarding predictors of psychotherapy outcome in general, including working alliance (Martin, Garske, & Davis, 2000) and length of treatment (Anderson & Lambert, 2001). In CBT for anxiety specifically, predictors of outcome include initial severity of symptoms (Kampman, Keijsers, Hoogduin, & Hendriks, 2007), interpersonal difficulties (Borkovec, Newman, Pincus, & Lytle, 2002), patient expectancies of positive outcome from treatment and treatment credibility (Price & Anderson, 2012), homework completion (Schmidt & Woolaway-Bickel, 2000), and therapist fidelity and competence in delivering the treatment protocol (Kazantzis, 2003, Kuyken & Tsivrikos, 2009).

Lower treatment effect sizes in older adults as compared to younger adults suggest that patient variables may play an important role in how one responds to treatment, although little research has examined predictors of outcome in older adults. Older adults differ from younger adults in that they are less likely to perceive the need for mental health services (Karlin, Duffy, & Gleaves, 2008) and may be less psychologically minded (e.g., Burgmer & Heuft, 2004), potentially indicating less positive expectancies for psychotherapy. Cognitive limitations in some older adults may produce difficulty in understanding or completing therapy tasks such as cognitive restructuring. Two prior studies have found that cognitive/executive functioning difficulties are associated with poorer response to CBT among older adults (Caudle et al., 2007, Mohlman, 2013). Less research has examined other potential factors that may predict outcome, but one study indicated that greater GAD severity, completion of more homework, and presence of a comorbid psychiatric diagnosis were associated with better CBT outcome among older adults (Wetherell et al., 2005).

Our team recently published results of a randomized controlled trial of CBT for late-life GAD in older adults (Stanley et al., 2014), which provides an opportunity to examine predictors of outcome among those who received CBT. In this study, CBT delivered by both expert, PhD-level providers (PLP) and non-expert, bachelor-level providers (BLP) led to significant improvements in GAD severity, anxiety, depression, insomnia, and mental health quality of life at post-treatment relative to usual care, with no differences in outcomes between the PLP and BLP conditions. In the current paper we conduct secondary analyses of these data to examine predictors of CBT outcome among the subset of participants receiving CBT. We collapsed PLP and BLP conditions into a single CBT condition. Given prior research, we expected that initial anxiety and depression severity, therapist adherence/competence, therapy credibility, number of sessions of CBT completed, and homework completion would predict outcome. Candidate predictors also included social support as a potential measure of interpersonal difficulties, and problem solving confidence, as CBT is a problem-focused therapy. Finally, we examined demographic characteristics including age, race/ethnicity, education, and medication status. Cognitive status was not examined as we only used a 6-item cognitive screener and excluded patients with cognitive difficulties, producing a restricted range of cognitive functioning.