Background: The way intellectual disability research is designed warrants critical examination, as the knowledge produced through these approaches informs evidence-based practices. People with lived experience should be considered experts in relation to understanding their bodies, conditions, and treatment.
Method: This systematic review analyses the design of Delphi studies, to determine the extent to which people with intellectual disability are involved as experts. The design of Delphi studies (involving structured feedback from experts) provides an insight into the extent that 'lived experience' is valued as a source of expert knowledge.
Results: Fifty-five publications reporting on forty-nine separate Delphi studies met our inclusion criteria. Nine publications report the involvement of people with intellectual disability. However, family/informal caregivers are represented as experts in higher numbers and their voices carry greater weight.
Conclusion: The findings of this review include guidance for practitioners and researchers to facilitate greater participatory roles of people with intellectual disability.
Keywords: evidence-based practice; expert; inclusive research; lived experience; participatory research.