JMIR Publications

ABSTRACT

Background:

Depression is a leading contributor to morbidity and disability among children and adolescents. Cognitive behavioural therapy (CBT) is a guideline-recommended first-line treatment, but access remains constrained by therapist supply, distance, and stigma. Smartphone-delivered Internet-based CBT (iCBT) has emerged as a scalable adjunct for adult populations, yet rigorous regulatory-grade evidence in Chinese paediatric and adolescent samples remains limited.

Objective:

This protocol describes a trial to determine whether a smartphone-delivered CBT-based digital therapeutic is superior to a matched health-education placebo in reducing depressive symptoms in Chinese children and adolescents with Major Depressive Disorder (MDD), and to characterize its safety.

Methods:

This is a prospective, multicenter, double-blind, placebo-controlled superiority trial at four tertiary-A hospitals in mainland China. Eligible children and adolescents aged 8–17 years meeting DSM-5 criteria for current MDD without psychotic features and scoring above 30 on the Children’s Depression Rating Scale–Revised (CDRS-R) at screening will be randomized 1:1 to an investigational smartphone-delivered CBT-based digital therapeutic (Model WL-PD) or to a visually matched health-education placebo. Both arms receive eight weeks of structured content; participants with moderate-to-severe severity (CDRS-R ≥ 57) additionally receive open-label fluoxetine under weight-banded dosing. The primary efficacy endpoint is the change in CDRS-R total score from baseline to Week 8. Secondary endpoints include CDRS-R change at Weeks 1, 2, 3, 4, and 6; response and remission rates; Clinical Global Impression scores; the Children’s Depression Inventory; the Conners’ Parent Symptom Questionnaire; and a Week-8 device-performance evaluation. Safety endpoints include adverse-event, serious adverse-event, and device-defect incidence. The planned sample of 214 participants (107 per arm) is powered at 80% to detect a between-arm difference of 4.6 CDRS-R points (assumed control SD = 10.7) with a one-sided α of 0.025 and 20% inflation for attrition. The primary analysis is an analysis of covariance on the Full Analysis Set adjusting for baseline CDRS-R; superiority is declared if the lower bound of the two-sided 95% confidence interval excludes zero, with a mixed model for repeated measures as a sensitivity analysis.

Results:

The trial was prospectively registered and opened to enrolment in March 2026; recruitment is ongoing, with a planned close in December 2026. The last enrolled participant’s Week-8 visit is expected in the first quarter of 2027, and the primary analysis is anticipated within the following calendar year.

Conclusions:

The blinded, multicentre design and the integration of guideline-concordant pharmacotherapy where indicated address two persistent gaps in the paediatric digital therapeutics literature: methodologically rigorous control conditions and pragmatic alignment with real-world prescribing. The trial will contribute registration-grade randomized evidence for a smartphone-delivered digital therapeutic in paediatric MDD. Clinical Trial: Chinese Clinical Trial Registry, ChiCTR2600120453 (prospectively registered on 16 March 2026). Protocol version V1.1, 26 January 2026 (sponsor identifier BJWL-202512).