Objective: No systematic review was identified investigating the influence of perceived therapist credibility on treatment outcomes. Extant treatment credibility reviews have focused on early perceptions without considering influence of various therapy phases. This study aimed to examine the relationship between perceived treatment and therapist credibility and treatment outcomes, while considering the timing of the credibility assessment as a potential moderator.
Method: Articles published in English peer-reviewed journals containing at least one quantitative measure of credibility and treatment outcome regarding face-to-face therapist-delivered interventions were eligible. PsycINFO, MEDLINE and Embase online databases were last searched on April 5th, 2023, and the Effective Public Health Practice Project tool was used to assess the study quality. Correlations between treatment credibility and outcomes, and therapist credibility were calculated separately.
Results: Analysis of 27 studies revealed a positive association between perceived treatment credibility and treatment outcome (r = 0.15,95%CI = 0.09,0.21,p < 0.001,n = 2061). Nine studies showed a strong association between perceived therapist credibility and outcome (r = 0.35,95%CI = 0.18,0.51;p < .001,n = 1161). No significant moderator found in both meta-analyses.
Conclusion: Findings suggest that clients' perceptions of higher credibility - whether concerning the treatment or the therapist - are associated with better therapeutic outcomes. Constraints in inclusion criteria and the small sample size in eligible studies were notable limitations.
Keywords: common factors; therapeutic relationship; therapist credibility; treatment credibility; treatment outcome.