Treatment Credibility as a Mechanism of Change in Cognitive Behavioral Therapy: Effects on Depression and Anxiety.

Objective: This study aimed to provide evidence for treatment credibility (TC) as a potential mechanism of change in cognitive behavioral therapy (CBT). Therefore, it focused on within-person effects that are free of the influence of stable characteristics and thus allow to exclude certain alternative explanations for the association under study. Method: The sample included 1,423 patients receiving outpatient CBT, who presented a wide variety of psychiatric diagnoses (mostly affective and anxiety disorders). TC, depression, and anxiety were measured every fifth session from Session 5 to 25 using the Credibility Expectancy Questionnaire (CEQ), the Patient Health Questionnaire–9 (PHQ-9), and the General Anxiety Disorder–7 (GAD-7), respectively. Symptom severity was assessed every session using the Hopkins Symptom Checklist–11. Within- and between-person effects of TC, depression, and anxiety were analyzed using the latent curve model with structured residuals (LCM-SRs). In exploratory analyses, within-person effects of TC on next-session symptom severity were assessed using a modification of the LCM-SR. Results: LCM-SRs exhibited excellent fit in main analyses. There were significant negative correlations of both intercepts and slopes (between-person level) of CEQ and PHQ-9 as well GAD-7. No significant cross-lagged effects (within-person level) were found over the five-session interval. However, session-wise analyses revealed significant cross-lagged effects of CEQ on Hopkins Symptom Checklist–11. Conclusions: This study is the first to find significant within-person effects of TC in session-wise analyses. This lends preliminary support to the notion of TC as a mechanism of change. The lack of significant findings at the five-session interval is discussed considering the specific design used in this study. What is the public health significance of this article?: This study did not find significant effects for treatment credibility on symptoms of depression and anxiety at a time interval of five sessions. However, in exploratory analyses significant effects of treatment credibility on next-session symptom severity were found. Thus, this study provides only preliminary evidence that treatment credibility has a negative causal effect on patients' symptom severity, meaning an increase in the patients' perception of treatment credibility may lead to an improvement of symptom severity. While more research is needed to support the findings of this study, we suggest that therapists pay attention to how credible patients perceive their treatment during the course of treatment and act accordingly in therapy phases in which patients lose confidence in their treatment, for example, by discussing the treatment rational or changing the treatment approach according to their patients' treatment beliefs. [ABSTRACT FROM AUTHOR]