BACKGROUND: Co-occurring self-harm and aggression (dual harm) is particularly prevalent among forensic mental health service (FMHS) patients. There is limited understanding of why this population engages in dual harm. AIMS: This work aims to explore FMHS patients' experiences of dual harm and how they make sense of this behaviour, with a focus on the role of emotions. METHOD: Participants were identified from their participation in a previous study. Sixteen FMHS patients with a lifetime history of dual harm were recruited from two hospitals. Individuals participated in one-to-one, semi-structured interviews where they reflected on past and/or current self-harm and aggression. Interview transcripts were analysed using reflexive thematic analysis. RESULTS: Six themes were generated: self-harm and aggression as emotional regulation strategies, the consequences of witnessing harmful behaviours, relationships with others and the self, trapped within the criminal justice system, the convergence and divergence of self-harm and aggression, and moving forward as an FMHS patient. Themes highlighted shared risk factors of dual harm across participants, including emotional dysregulation, perceived lack of social support and witnessing harmful behaviours. Participants underlined the duality of their self-harm and aggression, primarily utilising both to regulate negative emotions. These behaviours also fulfilled distinct purposes at times (e.g. self-harm as punishment, aggression as defence). The impact of contextual factors within FMHSs, including restrictive practices and institutionalisation, were emphasised. CONCLUSIONS: Findings provide recommendations that can help address dual harm within forensic settings, including (a) transdiagnostic, individualised approaches that consider the duality of self-harm and aggression
and (b) cultural and organisational focus on recovery-centred practice.