This article reports on a research synthesis of the relation between alliance and the outcomes of individual psychotherapy. Included were over 200 research reports based on 190 independent data sources, covering more than 14,000 treatments. Research involving 5 or more adult participants receiving genuine (as opposed to analogue) treatments, where the author(s) referred to one of the independent variables as "alliance," "therapeutic alliance," "helping alliance," or "working alliance" were the inclusion criteria. All analyses were done using the assumptions of a random model. The overall aggregate relation between the alliance and treatment outcome (adjusted for sample size and non independence of outcome measures) was r = .275 (k = 190); the 95% confidence interval for this value was .25-.30. The statistical probability associated with the aggregated relation between alliance and outcome is p < .0001. The data collected for this meta-analysis were quite variable (heterogeneous). Potential variables such as assessment perspectives (client, therapist, observer), publication source, types of assessment methods and time of assessment were explored.

The alliance continues to be one of the most investigated variables related to success in psychotherapy irrespective of theoretical orientation. We define and illustrate the alliance (also conceptualized as therapeutic alliance, helping alliance, or working alliance) and then present a meta-analysis of 295 independent studies that covered more than 30,000 patients (published between 1978 and 2017) for face-to-face and Internet-based psychotherapy. The relation of the alliance and treatment outcome was investigated using a three-level meta-analysis with random-effects restricted maximum-likelihood estimators. The overall alliance-outcome association for face-to-face psychotherapy was r = .278 (95% confidence intervals [.256, .299], p < .0001; equivalent of d = .579). There was heterogeneity among the effect sizes, and 2% of the 295 effect sizes indicated negative correlations. The correlation for Internet-based psychotherapy was approximately the same (viz., r = .275, k = 23). These results confirm the robustness of the positive relation between the alliance and outcome. This relation remains consistent across assessor perspectives, alliance and outcome measures, treatment approaches, patient characteristics, and countries. The article concludes with causality considerations, research limitations, diversity considerations, and therapeutic practices. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

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Prior meta-analyses have found a moderate but robust relationship between alliance and outcome across a broad spectrum of treatments, presenting concerns, contexts, and measurements. However, there continues to be a lively debate about the therapeutic role of the alliance, particularly in treatments that are tested using randomized clinical trial (RCT) designs. The purpose of this present study was to examine whether research design, type of treatment, or author's allegiance variables, alone or in combination, moderate the relationship between alliance and outcome. Multilevel longitudinal analysis was used to investigate the following moderators of the alliance-outcome correlation: (a) research design (RCT or other), (b) use of disorder-specific manuals, (c) specificity of outcomes, (d) cognitive and/or behavioral therapy (CBT) or other types of treatments, (e) researcher allegiance, and (f) time of alliance assessment. RCT, disorder-specific manual use, specificity of primary and secondary outcomes, and CBT did not moderate the alliance-outcome correlation. Early alliance-outcome correlations were slightly higher in studies conducted by investigators with specific interest in alliance than were those in studies conducted by researchers without such an allegiance. Over the course of therapy, these initial differences disappeared. Apart from this trend, none of the variables previously proposed as potential moderators or mediators of the alliance-outcome relation, alone or in combination, were found to have a mediating impact.