Identifying the Active Ingredients of a Behavioral-Activation-Based Digital Single-Session Intervention Targeting Depression

Digital single-session interventions (SSIs) have been shown to be effective in reducing myriad mental-health conditions. However, it is unclear which components of digital SSIs drive their therapeutic effects. In this study, we divided a well-evaluated behavioral-activation-based SSI into three candidate components—psychoeducation, testimonials, and action plan—each hypothesized to have independent therapeutic value. We conducted a 2 ³ factorial experiment ( N = 889) to evaluate effects of the individual components on depressive symptoms. Our results showed that only the action-plan candidate component had a significant main effect on depressive symptoms at 2-week (standardized mean difference [SMD] = −0.18) and 8-week (SMD = −0.12) follow-ups. In addition, users’ perceptions of the intervention’s credibility and their expectations of improvement immediately after completing it were significantly associated with a reduction in depressive symptoms at both time points. Our findings offer a more nuanced understanding of which elements in digital SSIs may drive their therapeutic benefits.