Effect evaluation of an mHealth intervention targeting health behaviors in early adolescence for promoting mental well-being (#LIFEGOALS): preregistration of a cluster controlled trial

This preregistration concerns the cluster controlled trial evaluating the effectiveness of the #LIFEGOALS intervention for promoting mental health in early adolescence. Adolescents can protect their mental health by increasing physical activity, reducing sitting time, getting sufficient sleep, and taking a daily breakfast. Targeting these lifestyle behaviors in young adolescents is an empowering, low-threshold approach that can create large public health effects. To target these behaviors, the mobile intervention #LIFEGOALS was developed in collaboration with stakeholders and users. The intervention is theory-based and consists of an application that includes a self-regulation component, a narrative, a chatbot, and other knowledge and features with the aim of motivating adolescents to adopt a healthy lifestyle. The current study will investigate the effects of the intervention on mental well-being using a group-controlled trial. Participants in the intervention group will install the #LIFEGOALS app on their phone and will be asked to use the app for 12 consecutive weeks. Participants in the control group do not receive an intervention but will only participate in the measurements. Outcomes will be assessed at baseline, 7 weeks after baseline (intermittent), and 13 weeks after baseline (post-test).