Attachment Orientations and Treatment Outcomes in Psychotherapy: Does the Alliance Mediate the Association?

Previous research has demonstrated associations between patients' attachment orientations and psychotherapy outcomes. Both theoretical and clinical literature suggest that the therapeutic alliance may serve as a mediator in this relationship. The present study investigated whether the therapeutic alliance mediates the connection between adult attachment and treatment outcomes in a clinical sample. One hundred eighteen patients diagnosed with major depressive disorder participated as part of a randomized controlled trial. Attachment orientation was assessed before treatment, and the therapeutic alliance and treatment outcomes were measured weekly throughout therapy. A multilevel mediation model tested whether the alliance mediated the connection between pretreatment attachment and depression improvement. Although the sample size was moderate compared with similar studies, the results did not support the proposed mediation model: The therapeutic alliance did not significantly mediate the relationship between attachment orientations and treatment outcomes. Exploratory response surface analysis using polynomial regression revealed a significant incongruence effect: patients with high avoidance and low anxiety experienced the greatest improvement in depression during therapy. This finding suggests that a specific attachment pattern (high avoidance, low anxiety) might explain previous mixed results in the literature.