Abstract Background Interventions targeting subthreshold depression (StD) are critically important for preventing major depressive disorder's onset. Our smartphone‐based, video‐viewing website (SPSRS), which presents positive word stimulation in videos, is a novel intervention for improving StD's depressive symptoms. Because no rigorous evidence exists for SPSRS's efficacy, this trial aims to evaluate the SPSRS intervention's efficacy on depressive symptoms. Methods The trial will be an evaluator‐blinded, randomized, 5‐week, parallel‐group superiority trial designed to assess whether the SPSRS intervention (experimental group) is effective compared to no intervention (waiting‐list control group). In a 1:1 ratio, 400 participants with StD will be randomly assigned to an experimental group ( n = 200) or a waiting‐list control group ( n = 200). The experimental group will receive a 10‐min SPSRS video‐viewing intervention once daily for 5 weeks; when the intervention ends, the waiting‐list control group will receive the treatment upon request. The intervention's primary outcome will be the mean change from baseline on the Center for Epidemiologic Studies Depression Scale; secondary outcomes will include the mean change from baseline on the Kessler Psychological Distress Scale and the Generalized Anxiety Disorder seven‐item scale. Result The results are presented according to the protocol. Discussion This trial's confirmation of SPSRS's efficacy could lead to new StD intervention strategies and provide interventions tailored to patient needs.
Uchida et al. (2026) studied this question.