Patients' perception of treatment credibility represents their belief about a treatment's personal logicality, suitability, and efficaciousness. Although long considered an important common factor bearing on clinical outcome, there have been no systematic reviews of the credibility-outcome association. The present study represents a meta-analysis of the association between patients' credibility perception and their posttreatment outcomes. To be included, articles published through August, 2017 had to (a) include a clinical sample, (b) include a therapist-delivered treatment of at least 3 sessions, (c) include a measure of patients' own early treatment credibility perception, (d) include at least 1 posttreatment mental health outcome not explicitly referenced as a follow-up occasion, and (e) report a statistical test of the credibility-outcome association. The meta-analysis was conducted on 24 independent samples (extracted from 19 references) with 1,504 patients. The overall weighted effect size was r ϭ .12, p Ͻ .001, or d ϭ .24, with high heterogeneity (I 2 ϭ 57%) and no evidence of publication bias. There were no significant moderating effects on the credibility-outcome association for any of the potential moderators that we evaluated. The meta-analytic findings are discussed in light of methodological limitations and with regard to their practice implications.
Clinical Impact StatementQuestion: This article examined the association between patients' perception of treatment credibility and their outcomes after treatment ends. Findings: Patients' treatment credibility belief is an empirically supported correlate of treatment outcome that therapists would do well to assess throughout treatment, attempt to heighten at treatment's outset, attempt to responsively match to intervention style, and respond to sensitively if/when it wanes. Meaning: The treatment credibilityimprovement correlation increases the scientific credibility of formerly ill-named "nonspecific" belief factors; thus, there is sufficient information to incorporate persuasive, credibility-enhancing strategies into treatment rationale delivery, ongoing clinical exchange, and training. Next Steps: Future research needs to (a) improve credibility measurement, (b) test strategies that causally enhance patients' perceptions of treatment and therapist credibility to improve treatment efficacy, and (c) illuminate both patient and therapist contributions to such credibility beliefs to help tailor clinical practice and training.