JMIR Publications

ABSTRACT

Background:

Adolescence is a critical period in the development of mental health problems. Emotion regulation (ER) is a transdiagnostic mechanism implicated across diverse mental health problems, and represents a promising target for early, scalable intervention. Self-directed digital cognitive behavioural therapy (CBT) interventions have the potential to extend access to mental health promotion and support; however, evidence regarding their acceptability, engagement and use among adolescents in real-world, non-clinical contexts remains limited.

Objective:

This study aimed to explore the acceptability, uptake and engagement of a self-directed digital CBT app targeting emotion regulation (MoodMission) among UK adolescents, and to identify subsequent early signals of change in both emotion regulation and mental health outcomes. Secondary objectives included assessing the feasibility of evaluating this type of intervention within a school setting.

Methods:

A convergent mixed-methods pre-post cohort design was employed. Adolescents were recruited from one secondary school in England and offered access to the MoodMission app for six weeks. Quantitative data included app uptake, in-app engagement metrics, study retention, and changes in emotion regulation and mental health, measured using the Difficulties in Emotion Regulation Scale (DERS), the Emotion Regulation Questionnaire (ERQ), and the Depression, Anxiety and Stress Scale (DASS). Generalised eta squared (η²G) effect sizes were calculated to explore the magnitude of change. Qualitative data were collected via semi-structured focus groups with adolescents who engaged and did not engage with the app and were analysed using inductive thematic analysis to capture experiences, perceived acceptability, and barriers to engagement.

Results:

Of 43 adolescents completing baseline measures, 11 (25.6%) downloaded the app and 8 (18.6%) completed at least one in-app activity. Participants spent a mean of 15.34 seconds (SD 10.99) per activity and reported moderate perceived usefulness (mean 6.99/10), with emotion- and behaviour-based activities rated as most helpful. Attrition was at expected levels for self-directed digital interventions, with 7 participants retained at the 6-week follow-up (overall attrition rate 83.7%). Qualitative findings highlighted four key themes: a preference for human and relational support over digital tools, difficulty engaging with the app during periods of high emotional intensity, the importance of personalisation and inclusivity, and the need for emotional clarity to use self-directed interventions effectively.

Conclusions:

Findings underscore the importance of co-design, personalisation, and integration of human support when developing digital mental health interventions for adolescents. Given increased messaging about the lack of safety in digital media and the growing bans on adolescent media use, future research should explore blended models of mental health promotion co-designed with adolescents, combining brief digital tools with face-to-face support from trusted adults or peers that are more appropriate and acceptable.