Abstract
Universal school-based mental health interventions involve delivering mental health content to all young people within a class, regardless of need. They are typically evaluated in terms of average effects, yet there is growing evidence that individual young people may experience the same intervention very differently. In this narrative review, we consider five illustrative sources of individual variation in response to universal school-based mental health interventions: social relationships within the classroom, baseline mental health status, special educational needs and disabilities (SEND), family circumstances and gender. For each factor, we review relevant theoretical and empirical literature to explore how each factor might contribute to positive, negative and/or neutral experiences during universal school-based mental health interventions. The review is additionally informed by reflections from a Young People’s Advisory Group of five 14–18-year-olds with experience of school mental health lessons, whose perspectives are integrated throughout. We conclude that understanding individual variability is crucial for evaluating the safety and effectiveness of universal school-based mental health interventions, and for determining whether and how these interventions can be adapted to meet the diverse needs of young people.