Engaging adults with severe mental illness in research: considerations and practical recommendations for meaningful patient and public involvement

BACKGROUND: Patient and public involvement (PPI) in mental health research is essential but presents unique challenges, particularly when engaging adults with severe mental illness (SMI). This report focusses on the process, benefits, and challenges of involving adults with lived experience of SMI as active partners within a five-year research programme aimed at co-producing a new evidence- and theory-based intervention to support smoking behaviour change following mental health inpatient care. It summarises our PPI strategy, the lived experience insight provided, and practical recommendations for facilitating meaningful involvement of people with SMI throughout the research process. METHODS: We reflect on our approach to PPI within the research programme. Involvement spanned the entire research programme, from intervention design to dissemination. The research team reflected on the PPI participants' experience via informal feedback, meeting notes, and reflective team discussions. These reflections informed the identification of practical considerations and recommendations. RESULTS: PPI was crucial to the research and had a powerful, meaningful impact, with group members playing a key role in shaping participant-facing materials and intervention resources. Success was supported by early planning, dedicated facilitation, sustained relationship-building, and clear communication. Challenges included balancing meaningful input with accessibility, accommodating individual needs and preferences, and supporting varying levels of engagement due to participants' ongoing mental health experience. CONCLUSION: Involving adults with SMI in research is both feasible and valuable, and requires careful planning, flexibility, and support. This report highlights the importance of relational approaches and tailored support to enable meaningful contributions, offering practical guidance for researchers developing inclusive PPI strategies in mental health trials involving complex populations.