King's College London

We have evaluated a novel early intervention for adolescent depression (age 16–18) in a feasibility randomised controlled trial. This nested process evaluation aimed to understand how this complex intervention worked. We sought to understand participants’ views and experiences of receiving and interacting with the intervention to evaluate whether the underpinning theoretical basis of the intervention is justified and whether it contributes to valued outcomes for participants. Twelve participants were invited to take part in semi-structured interviews. Framework analysis was employed to identify important aspects of adolescents’ experiences. The active ingredients identified by participants were consistent with and extended our understanding of the theoretical basis of the intervention. Four principle themes were identified: understanding how memory works and being able to remember memories in more detail; processing negative experiences and letting go; imagining positive future events; and understanding and being kinder to myself. The outcomes of the intervention were valued by participants. Six principle themes were identified: improving mood and well-being; reducing impact of negative memories; motivation and goal-directed behaviour; overcoming avoidance and rumination; relationships, communication and being open; and self-understanding and acceptance. A simplified logic model is also proposed to connect the intervention components, active ingredients, and valued outcomes. The findings provide an in-depth understanding of how participants interacted with the intervention and what they derived from it. For example, the findings establish processing negative experiences as a core intervention component, extend it to include letting go of these memories, and highlight that reducing the impact of negative memories is valued by participants. This richer understanding guides further intervention development and future implementation.