Ambivalence as a Moderator of Treatment Outcomes in Motivational Interviewing and Cognitive Behavioural Therapy for Generalized Anxiety Disorder

Although there is a robust finding documenting the efficacy of Cognitive Behavioural Therapy (CBT) in treating anxiety, a significant proportion of clients fail to respond optimally to treatment. A major focus of psychotherapy research involves client-treatment matching, which examines client characteristics as potential predictors of treatment response. Client ambivalence has been identified as a key marker in psychotherapy with wide-ranging implications for engagement in therapy. Motivational Interviewing (MI) has strong empirical support for increasing client commitment for change through the resolution of ambivalence. Though it may be speculated that integrating MI into CBT may be more efficacious for clients high in ambivalence than CBT alone, the investigation of these critical client-treatment matching research questions has been hampered by inadequate measures of ambivalence. This study sought to examine this question in the context of CBT alone versus MI-CBT for 85 clients with severe generalized anxiety disorder (GAD). Rather than relying on self-report, the study used an observational measure (client in-session talk against change) to quantify ambivalence. Findings suggest MI-CBT resulted in better long-term worry outcomes than CBT alone for clients who were high in early ambivalence, whereas clients low in early ambivalence did better with CBT alone. In other words, client ambivalence significantly moderated treatment outcomes. In contrast, there was no moderation effect of ambivalence on interpersonal problems. Here, results revealed that regardless of their early ambivalence levels, clients who received MI-CBT reported significantly fewer interpersonal problems at long-term follow-up than clients receiving CBT alone. Client ambivalence seems to represent a key individual difference variable, and tailoring standard CBT protocols to incorporate MI may be particularly efficacious for clients who are highly ambivalent about change. The results also emphasize the potentially broader benefits of MI, in that, integrating MI into CBT may be an effective way of reducing interpersonal problems for all clients, regardless of their early ambivalence levels. Overall, these findings support the benefit of systematic training in identifying and flexibly responding to in-session markers of client change language, and suggest that treatment outcomes can be improved by training CBT therapists to incorporate the MI spirit during moments of ambivalence.