Study protocol for a pilot randomized controlled trial on a smartphone application-based intervention for subthreshold depression Study protocol clinical trial (SPIRIT Compliant)

Introduction: Interventions aimed at addressing subthreshold depression (StD) are important to prevent the onset of major depressive disorder. Our video playback application (SPSRS) is designed to reduce depressive symptoms by presenting positive words in videos, shedding new light on the treatment of StD. However, no randomized controlled trial (RCT) has utilized this video playback application for the treatment of individuals with StD. Therefore, a pilot RCT was designed to determine the feasibility of a full-scale trial. We herein present a study protocol for investigating the utility of a video playback application intervention for individuals with StD. Methods: This 5-week, single-blind, 2-arm, parallel-group, pilot RCT will determine the effectiveness of the video playback application by comparing individuals who had and had not been exposed to the same. A total of 32 individuals with StD will be randomly assigned to the experimental or control group at a 1:1 ratio. The experimental group will receive a 10-minute intervention containing the video playback application per day, whereas the control group will receive no intervention. The primary outcome will include changes in the Center for Epidemiologic Studies Depression Scale score after the 5-week intervention, while secondary outcomes will include changes in the Kessler Screening Scale for psychological distress and the generalized anxiety disorder 7-item scale score after the 5-week intervention. Statistical analysis using linear mixed models with the restricted maximum likelihood estimation method will then be performed. Discussion: This pilot RCT will have been the first to explore the utility of SPSRS application interventions that display positive words in videos for individuals with StD. The results of this pilot trial are expected to help in the design and implementation of a full-scale RCT that investigates the effects of SPSRS applications among individuals with StD.