Interpersonal agency as predictor of the within-patient alliance effects on depression severity

Several studies have reported significant within-patient effects of the therapeutic alliance on outcome. However, it remains uncertain whether there are specific patient groups for whom an improved alliance might be particularly beneficial. The relational nature of the alliance makes patients' interpersonal problems a promising candidate for examining such differential effects. This study aims to analyze (i) between- and within-patient effects of the alliance on depression severity, (ii) the effects of patients' baseline interpersonal problems on the within-patient alliance-outcome association, and (iii) whether within-patient effects of the alliance remain significant when adjusting for patients' initial interpersonal problems.

A sample of 141 patients with depression and undergoing outpatient psychotherapy completed the Inventory of Interpersonal Problems at baseline as well as a brief version of the Working Alliance Inventory and the Well-Being Index (as a proxy of depression severity) session by session.

Multilevel models revealed both significant between- and within-patient effects of the alliance on improvements in depression severity. Patients' problems relating to agency had a significant effect on the within-patient effect of alliance, with more submissive patients benefiting more from an improved therapeutic alliance. Finally, the between- and within-patient effects of the alliance remained significant when adjusting for the patients' agentic interpersonal problems and treatment condition.

The results provide evidence on which types of patients would particularly benefit from an improved therapeutic alliance. For patients suffering from low interpersonal agency and reporting problems with submissiveness, an enhanced alliance during the therapy process might improve treatment outcome. (PsycINFO Database Record (c) 2020 APA, all rights reserved).