Optimizing Expectations in an Internet- and mobile-based Intervention for Depression: Study Protocol for a Randomized Factorial Trial

Background: Expectations are considered an important mechanism of change in psychotherapeutic interventions, including Internet- and mobile-based interventions (IMI). This study aims to investigate whether two expectation-focused micro-interventions can enhance the effects of an IMI for participants with elevated depression.Methods: All participants will receive an established IMI consisting of six evidence-based cognitive behavioral modules. In this 2x3 factorial design, 720 adult participants will be randomized to receive (1) either the IMI in standard or personalized framing (first randomization factor), in combination with (2) an expectation-focused telephone call mid-treatment, a supportive phone call or no phone call (second randomization factor). The primary outcome is depression at mid- and post-treatment (BDI-II). Secondary measures include expectations, adherence, state and trait anxiety and depression, disability, negative effects, and satisfaction with treatment. Discussion: This study will increase knowledge about applying micro-interventions to modify expectations and improve the effects of IMI in the treatment of depressive symptoms. Scalable IMI have the potential to improve healthcare but ways to further improve their effects and adherence need to be explored.Trial registration: The trial was prospectively registered under DRKS00032982.