Which methodologies and methods should be used for psychosocial intervention research in dementia? Protocol for a stakeholder-driven, multi-method Delphi study.

introductionPsychosocial interventions are essential to support people living with dementia and their carers. A consensus on what is most important for research on psychosocial intervention in dementia and how intervention studies should best be conducted is currently lacking. This protocol describes the research plan aimed at achieving consensus on (i) the relevance of core elements (CEs) for the development, feasibility testing/piloting, evaluation and/or implementation phases of psychosocial interventions in dementia and (ii) methodologies (eg, design) and methods most suitable to address CEs per phase. METHODS AND ANALYSIS: This study was co-designed with a multi-stakeholder advisory group and a multi-disciplinary INTERDEM (psychosocial INTERventions in DEMentia) Methodology Taskforce steering committee. It will involve a multi-phase modified Delphi design, including surveys and group discussions with stakeholders, namely people living with dementia, (informal/unpaid/family) carers, health and social care professionals, policy makers, representatives from insurance companies and psychosocial researchers. A series of iterative 'rounds' will be conducted. In round 1 (Phase 1: 'identification'), stakeholders will be asked to complete an online survey rating the importance of CEs from the UK Medical Research Council (MRC) Framework, namely (i) consider context; (ii) develop, refine and (retest) programme theory; (iii) engage stakeholders; (iv) identify key uncertainties; (v) refine interventions and (vi) economic considerations per phase; propose relevant additional CEs and list methodologies/methods that most suitably address CEs. These ratings will be further explored through online discussion rounds (Phase 2: 'elaboration'). In round 2 (Phase 3: 'consensus'), participants will be asked to rate the importance of CEs again (ie, new CEs and where no consensus was reached in Phase 1) and the usefulness of methodologies/methods to address CEs. Outcomes will be discussed with the advisory group and steering committee (Phase 4: 'validation'). This process (Phases 3 and 4) will be repeated until a consensus on CEs and methodologies/methods is achieved. ETHICS AND DISSEMINATION: Ethical approval was received at Maastricht University (FHML-REC/2025/078) and the University of West London (UWL/REC/SBS-01195). Participants will sign informed consent prior to study participation. Results will be disseminated through a peer-reviewed publication, seminars, webinars, conferences, postgraduate dementia programmes, blogs, commissioner briefings and social media. STUDY REGISTRATION: Open Science Framework (https://doi.org/10.17605/OSF.IO/DQRFA).