Therapist effects in the therapeutic alliance-outcome relationship: a restricted-maximum likelihood meta-analysis

Although the relationship between the therapeutic alliance and outcome has been supported consistently across several studies and meta-analyses, there is less known about how the patient and therapist contribute to this relationship. The purpose of this present meta-analysis was to (1) test for therapist effects in the alliance-outcome correlation and (2) extend the findings of previous research by examining several potential confounds/covariates of this relationship.

A random effects analysis examined several moderators of the alliance-outcome correlation. These included (a) patient-therapist ratio (patient N divided by therapist N), (b) alliance and outcome rater (patient, therapist, and observer), (c) alliance measure, (d) research design and (e) DSM IV Axis II diagnosis.

The patient-therapist ratio (PTR) was a significant moderator of the alliance-outcome correlation. Controlling for several potential confounds in a multi-predictor meta-regression, including rater of alliance, research design, percentage of patient Axis II diagnoses, rater of outcome and alliance measure, PTR remained a significant moderator of the alliance-outcome correlation.

Corroborating previous research, therapist variability in the alliance appears to be more important than patient variability for improved patient outcomes. This relationship remains significant even when simultaneously controlling for several potential covariates of this relationship.