Mechanisms of Change in the Treatment of Depression: On the Role of Attachment, Reappraisal and Suppression.

Identifying mechanisms of change in psychotherapy is imperative to optimize treatment effectiveness for depression. Research has identified specific mechanisms, primarily in outpatient pathology. However, the transdiagnostic robustness of these mechanisms remains to be quantified in more severely affected populations. This study aims to delineate the role of anxious and avoidant attachment, expressive suppression and cognitive reappraisal as within-person mechanisms of change in inpatient schema therapy and cognitive behaviour therapy for patients acutely and severely affected by major depressive disorder. A secondary analysis of a randomized clinical trial in an intensive multimodal inpatient and day-clinic setting with 198 patients was conducted. To differentiate stable between-person traits from therapeutic within-person shifts, Bayesian random-intercept cross-lagged panel models were employed. The data provided evidence that schema therapy and cognitive behaviour therapy do not differentially affect the mechanisms of change, that these mechanisms do not predict subsequent symptom change and that they do not mediate treatment effects on depressive symptoms. In contrast, a significant reverse association was identified: Symptom reduction was associated with subsequent improvements in cognitive reappraisal and expressive suppression. This temporal precedence suggests that alterations in cognitive reappraisal and expressive suppression are consequences of change in depressive symptoms rather than its primary drivers. These insights could guide researchers and clinicians in future investigations towards precision psychotherapy, directing attention not only to what interventions are performed but also to when they are performed.