How Central Is the Alliance in Psychotherapy? A Multilevel Longitudinal Meta-Analysis Christoph Flu ¨ckiger University of Bern and University of Wisconsin—Madison A. C. Del Re University of Wisconsin—Madison and Veterans Affairs Long Beach Healthcare System, Long Beach, California Bruce E. Wampold University of Wisconsin—Madison and Research Institute, Modum Bad Psychiatric Center, Vikersund, Norway Dianne Symonds Kwantlen Polytechnic University Adam O. Horvath Simon Fraser University 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 corre- lation: (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. Keywords: therapeutic alliance, alliance– outcome correlations, multilevel longitudinal meta-analysis There is a growing body of evidence that the quality of the therapeutic alliance is linked to the success of treatment across a broad section of clients, treatments, and identified problems. The relation between alliance and outcome is modest, approx- imately 7% of the variance, but this link has proven to be robust across four meta-analyses conducted over the past 20 years (Horvath & Bedi, 2002; Horvath, Del Re, Flu ¨ckiger, & Sy- monds, 2011a, 2011b; Horvath & Symonds,1991; Martin, Gar- ske, & Davis, 2000). Moreover, though the correlational link is not very large, it is greater than the relation reported between other treatment variables such as therapist adherence to treat- ment manual, competence and outcome (Webb, DeRubeis, & Barber, 2010). The relation between alliance and outcome appears to be ubiq- uitous across different types of treatments, but there is an ongoing controversy about the relative importance of the alliance, particu- larly in treatments that are tested using a randomized clinical trial (RCT) design (e.g., Crits-Christoph, Wilson, & Hollon, 2005; DeRubeis, Brotman, & Gibbons, 2005; Strunk, Brotman, & De- Rubeis, 2010). The clinical aspects/implications of this debate are important: Advocates of specific factors, for example Siev, Hup- pert, and Chambless (2009), have argued that the alliance is relatively unimportant in some therapies, whereas it is a specific treatment technique in others (e.g., in relationship-based thera- pies). On the other side of the debate, the argument is made that the alliance is a measure of the therapists’ and clients’ mutual engage- ment in the work of therapy regardless of the specific treatments or problems involved and thus represents an important component for This article was published Online First October 10, 2011. Christoph Flu ¨ckiger, Department of Clinical Psychology and Psychother- apy, University of Bern, Bern, Switzerland, and Department of Counseling Psychology, University of Wisconsin—Madison; A. C. Del Re, Department of Counseling Psychology, University of Wisconsin—Madison, and Veterans Affairs Long Beach Healthcare System, Long Beach, California; Bruce E. Wampold, Department of Counseling Psychology, University of Wisconsin— Madison, and Research Institute, Modum Bad Psychiatric Center, Vikersund, Norway; Dianne Symonds, Department of Nursing Science, Kwantlen Poly- technic University, Surrey, British Columbia, Canada; and Adam O. Horvath, Faculty of Education and Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada. This article is based on the data set presented by Horvath, Del Re, Flu ¨ckiger, and Symonds (2011b), Alliance in Individual Psychotherapy, in J. C. Norcross (Ed.), Psychotherapy relationships that work: Evidence- based responsiveness (2nd ed.). New York, NY: Oxford University Press. This research was supported by Swiss Science National Foundation Grant PA00P1-124102 awarded to Christoph Flu ¨ckiger. Correspondence concerning this article should be addressed to Christoph Flu ¨ckiger, University of Bern, Department of Clinical Psychology and Psychotherapy, Gesellschaftsstrasse 49, CH-3012 Bern, Switzerland. E-mail: christoph.flueckiger@psy.unibe.ch Journal of Counseling Psychology © 2011 American Psychological Association 2012, Vol. 59, No. 1, 10 –17 0022-0167/11/$12.00 DOI: 10.1037/a0025749 10