<![CDATA[Introduction: Unhealthy lifestyle behaviours in adolescence are major risk factors for non-communicable diseases. Digital interventions may provide age-appropriate support for preventive health efforts in this population. This review aimed to evaluate the effectiveness of digital interventions in improving adolescent lifestyle behaviours related to non-communicable disease prevention, particularly physical activity, dietary behaviour, sedentary behaviour, and weight-related lifestyle outcomes. Methods: A systematic search was conducted in PubMed, Scopus, Web of Science, and ScienceDirect to identify randomised controlled trials evaluating digital health interventions in adolescents. Two reviewers independently performed study selection and data extraction in accordance with PRISMA guidelines. Data on intervention characteristics, technological platforms, behaviour change strategies, and reported behavioural outcomes were extracted. Methodological quality was assessed using the Joanna Briggs Institute critical appraisal checklist. Results: Eleven randomised controlled trials were included. Interventions were delivered through mobile health applications, wearable monitoring devices, chatbot-based coaching, virtual reality, and web-based programmes. The most consistent findings were observed for physical activity and fitness-related outcomes, although effects were not uniform across studies. Evidence for dietary behaviour was generally favourable but varied, whereas evidence for sedentary behaviour and weight-related outcomes remained limited or mixed. Interventions incorporating self-monitoring, goal setting, gamification, and personalised feedback appeared more likely to support behavioural engagement. Conclusions: Digital interventions may support improvements in adolescents' health behaviours, particularly physical activity. Future studies should prioritise longer follow-up periods, stronger engagement strategies, and the integration of digital tools within broader health promotion environments.]]>
