One Size Does Not Fit All: Examining Heterogeneity and Identifying Moderators of the Alliance–Outcome Association

Although the alliance–outcome association is one of the most consistent findings in psychotherapy research, it is also highly heterogeneous. Little is known about the factors explaining this variability, and consequently there is a lack of adequate knowledge about how to utilize this association to improve treatment. The present study had the following objectives: (a) to examine the associations between within- and between-individual variability in alliance and outcome, controlling for previous symptomatic levels; (b) to examine the duration of the alliance–outcome association; and (c) to examine potential moderators of the alliance–outcome association. A total of 547 patients treated in a primary care psychotherapy setting in Chile were randomly assigned to 5 feedback conditions. The alliance–outcome association was analyzed using multilevel models, disentangling changes in alliance within-individuals from alliance between-individuals. Patient and therapist characteristics were examined as potential moderators. Findings suggest that patients who reported a better early alliance also reported a better outcome. Furthermore, patients reporting time-specific improvement in alliance also reported a greater reduction in symptoms. The unique effect of alliance on outcome at one point in time is maintained for a period of 2 weeks. Patients with more severe symptoms and longer treatments benefited more from a good alliance. Therapists identifying themselves as more integrative in their treatment orientation were able to better utilize good alliances for treatment success. Finally, the size of the alliance–outcome association can be manipulated by feedback to therapists.