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.