The Card Sort Task for Self-harm (CaTS): a review of the development, application, and adaptation of a novel tool for the assessment and contextual understanding of self-harm

Developing clear, adaptable, and engaging methodologies is critical for advancing the understanding and prevention of self-harm and suicide. This paper presents a review of the development, application and adaptation of the Card Sort Task for Self-Harm (CaTS), a structured, interactive tool designed to map individual pathways to self-harm. Grounded in psychological theory and co-developed with input from people with lived experience, CaTS uses 117 evidence-informed cards representing thoughts, feelings, events, behaviours, and support-related factors. Participants place these cards along a timeline spanning the period before and after a self-harm episode, enabling the identification of both risk and protective factors as well as the sequencing of relevant experiences. The inclusion of blank cards supports personalisation, ensuring the tool remains sensitive to diverse experiences. Unlike traditional psychometric measures, CaTS emphasises holistic understanding and temporal patterning. Since its initial application, CaTS has been adapted for use with varied populations, delivery formats, and research settings. This paper outlines the conception and evolution of CaTS, highlighting the tool's potential for clinical, research and participatory applications, and utility in training and public engagement. By offering a flexible, person-centred approach, CaTS advances inclusive and nuanced exploration of self-harm processes, offering a novel way to explore often-overlooked, complex temporal dynamics.