Effects of a Digital Parent-Child Single-Session Growth Mindset Intervention on Adolescent Depression and Anxiety Symptoms: A Three-Arm Waitlist Randomized Controlled Trial.

Adolescent depression and anxiety are prevalent, yet brief and scalable parent-child digital interventions remain understudied. This study evaluated the effects of a digital parent-child single-session growth mindset intervention targeting beliefs about intelligence, failure, and emotion on adolescent internalizing of symptoms. In a three-arm waitlist cluster randomized controlled trial, 390 parent-child dyads from seven secondary schools in Hong Kong were assigned to a parent-child intervention group, a child-only intervention group, or a waitlist control group. Students were assessed at baseline, 2 weeks, and 3 months, and parents at baseline and 3 months. Cluster-adjusted generalized estimating equations were used for intention-to-treat analyses. A significant time-by-group interaction was observed for child-reported depression, whereas the interaction effects for other outcomes were non-significant. However, cluster-adjusted baseline differences across groups limited attribution of changes in depression to intervention effects. Relative to controls, the parent-child intervention descriptively showed short-term improvement in hopelessness and sustained gains in child-reported parent-child relationships over 3 months. Moderation analyses suggested clearer short-term benefits among adolescents with higher baseline symptoms and among girls. Overall, the PC-SMILE intervention in this study did not show statistically significant effect on reducing internalizing symptoms. Improvement on intervention design and implementation would benefit further refinement of brief, scalable parent-child digital interventions. Trial registration: ClinicalTrials.gov NCT05493865.