Therapeutic alliance mediates the association between personality and treatment outcome in patients with major depressive disorder.
BACKGROUND
Patient personality traits have been shown to influence treatment outcome in those with major depressive disorder (MDD). The trait agreeableness, which reflects an interpersonal orientation, may affect treatment outcome via its role in the formation of therapeutic alliance. No published studies have tested this hypothesis in patients with MDD.


METHOD
Participants were 209 outpatients with MDD who were treated in a randomized control trial. Mediation analyses were conducted to examine the role of therapeutic alliance in the association between pretreatment personality and the reduction of depression symptom severity during treatment. Separate models were estimated for patient- versus therapist-rated therapeutic alliance.


RESULTS
We found a significant indirect effect of agreeableness on the reduction of depression severity via patient-rated therapeutic alliance. Results were replicated across two well-validated measures of depression symptom severity. Results also partially supported indirect effects for extraversion and openness. Therapist ratings of alliance did not mediate the association between personality and treatment outcomes.


LIMITATIONS
Patients were recruited as part of a randomized control trial, which may limit the generalizability of results to practice-based clinical settings. Due to constraints on statistical power, intervention-specific mediation results were not examined.


CONCLUSIONS
These results highlight the importance of personality and the role it plays in treatment process as well as outcome.