Unpacking the chain of change in group CBT and ACT for depression: A protocol for a randomized clinical trial

Cognitive behavioral therapy (CBT) and acceptance and commitment therapy (ACT) are among our most effective treatments for depression, yet their efficacy remains modest. Prior research has not been able to improve these efficacy rates in part due to the limited insight into the processes of change in these treatments and which individuals may benefit more or less from different therapeutic processes.

One hundred adults with a diagnosis of major depressive disorder will be randomized to receive eight weeks of group CBT (n = 50) or ACT (n = 50). We will use intensive longitudinal sampling methods to examine therapeutic skills use, theorized treatment mechanisms, and treatment outcomes throughout the course of treatment. The primary aim is to examine the mediational effect of theorized treatment mechanisms on the association between therapeutic skills use and treatment outcomes. Our secondary aim is to examine the combined moderating effects of treatment modality and client characteristics on the association between therapeutic skills use and activation of mechanisms of change.

This work has the potential to inform precision mental health care by closing in on the question of "what works and for whom" as it relates to data-driven psychotherapeutic interventions for depression.

The study is registered at www.

gov (NCT06245096).