Cognitive behavioral therapy skills via a smartphone app for subthreshold depression among adults in the community: the RESILIENT randomized controlled trial

Subthreshold depression, characterized by depressive symptoms that do not fully meet diagnostic criteria for major depressive disorder, affects about 11% of the global population and is linked to impaired social function, reduced quality of life, increased healthcare utilization, and higher mortality. Individuals with subthreshold depression are three times more likely to develop a major depressive episode than those without. This trial investigated whether specific components of cognitive behavioral therapy (CBT) promote mental health by developing a smartphone app with five representative CBT skills: behavioral activation (BA), cognitive restructuring (CR), problem-solving (PS), assertion training (AT), and behavior therapy for insomnia (BI). Using a master randomized design with four 2×2 factorial trials, the study recruited 3,936 adults with subthreshold depression (September 2022–February 2024). Follow-up at week 6 was 97%; adherence to the app was 84%. All CBT skills and their combinations significantly outperformed three control conditions (delayed treatment, health information, self-check). Effect sizes (standardized mean differences, SMD) for PHQ-9 change from baseline to week 6 ranged between -0.67 (95% CI: -0.81 to -0.53) and -0.16 (-0.30 to -0.02). These findings identify active CBT ingredients to inform design of scalable, effective psychotherapies.