Mechanism engagement as a potential evidence-based approach to personalized treatment termination.

Objective: This study explores whether early change on a putative mechanism maintaining symptoms can serve as a proximal indicator of response to prompt discontinuation. Method: Patients (N = 70; Mage = 33.74, 67% female, 74% white) with heterogeneous anxiety and depressive disorders completed a sequential multiple assignment randomized trial (SMART). Patients received 6 sessions of skill modules from the Unified Protocol and then underwent a second-stage randomization to either receive the remaining 6 sessions (Full duration) or discontinue treatment (Brief duration). All participants completed weekly self-report measures of anxiety and depressive symptoms and distress aversion for the full 12-week treatment window. We used structural equation modeling to test (1) if distress aversion demonstrated significant variability during the first-stage randomization and (2) if distress aversion during the first-stage randomization predicted second-stage changes in anxiety and depression. Results: Participants demonstrated significant variability in first-stage distress aversion. Latent distress aversion slopes significantly predicted latent second-stage anxiety slopes, whereas latent distress aversion intercepts significantly predicted latent second-stage depression slopes. Conclusions: These results suggest that early mechanism engagement may have potential as a trigger to prompt personalized termination. Shorter courses of care may reduce patient costs and increase the mental health service system's capacity.