Discussion
Our primary aim was to examine the associations between personality, therapeutic alliance, and treatment outcome in a sample of patients receiving one of three empirically supported treatments for MDD. Mediation analyses revealed significant indirect effects for agreeableness via therapeutic alliance. Results were replicated across two well-validated measures of depressive symptom severity. We also found support for indirect effects of extraversion and openness, but these were uniquely mediated through late ratings of alliance. This represents the first investigation to test empirically the hypothesis that patient personality influences treatment outcome via its influence on therapeutic alliance among patients with MDD