RESUMEN
BACKGROUND: Involving the public in evidence synthesis research is challenging due to the highly analytic nature of the projects, so it is important that involvement processes are documented, reflected upon, and shared to devise best practices. There is a literature gap on the involvement of the public in individual participant data meta-analyses, particularly in public health projects. We aimed to document and reflect on our collective experiences of involving and being involved as public stakeholders at all stages of a systematic review and individual participant data meta-analysis project. METHODS: We formed a stakeholder group made of four members of the public at the beginning of our evidence synthesis project comprising a systematic review, an aggregate data meta-analysis, and an individual participant data meta-analysis of mindfulness-based programmes for mental health promotion in non-clinical adults. Following each group meeting, members and participating researchers completed written reflections; one group member collected and collated these. At the end of the project, a reflective writing workshop was held before all members completed their final reflections. Everyone completed an adapted, open-ended questionnaire which asked about what did and did not work well, the overall experience, what could be improved, and the felt impact the stakeholder group had on the research. RESULTS: Overall, the stakeholders and researchers reported a positive experience of working together. Positives from the stakeholders' point of view included learning new skills, experiencing research, and making new friends. For the researchers, stakeholders helped them focus on what matters to the public and were reinvigorating research partners. The challenges stakeholders experienced included having long gaps between meetings and feeling overwhelmed. The researchers found it challenging to strike the balance between asking stakeholders to be involved and for them to learn research-related skills without overburdening them and making sure that the learning was engaging. When looking back at their experience, stakeholders described seeing their impact on the project in hindsight but that this was not felt while the project was being carried out. CONCLUSION: Successfully involving the public in complex evidence synthesis projects is possible and valuable from the points of view of the researchers and the stakeholders. However, it requires a significant time, skill, and resource investment that needs to be factored in from project inception. Further guidance and stakeholder training materials would be helpful. Specific suggestions are provided.