Beyond effectiveness: orienting youth mental health research towards population impact

Youth mental health problems are a major and growing global challenge. Although effective interventions exist for many common mental health problems, population-level improvements have been limited. This paradox highlights that intervention effectiveness alone is likely insufficient to generate meaningful public health impact. Interventions must also reach young people, be adopted by services and practitioners, be delivered with quality, and be sustained over time. Drawing on implementation science, we argue that youth mental health research should ask not only "Does this intervention work?" but also "Can this intervention generate population-level impact?". We illustrate how impact considerations can be embedded throughout the intervention lifecycle. First, we discuss designing for reach and adoption, using single-session interventions as an example of scalable approaches aligned with real-world patterns of service use. Second, we highlight the importance of evaluating effectiveness under routine conditions, drawing on a trial of a modular treatment in outpatient child and adolescent clinics as an example of generating externally valid evidence. Third, we emphasise the need to study implementation and sustainment, using examples from national mental health programmes and implementation research initiatives. To reduce the burden of youth mental health problems, implementation, reach, and sustainment must be treated as core objectives if our work is to have population-level impact.