Importance: Communicating clearly about who is included in a population group is a critical element to effective dissemination and knowledge transfer. This narrative review highlights the inconsistency as it relates to communicating about individuals with intellectual disability (ID) and developmental disability (DD).
Observations: There is enormous variability in the use of definitions and abbreviations in the field of intellectual disability and developmental disabilities. The lack of consistency has resulted in widely varying reported rates of prevalence and has contributed to confusion around the interpretation of research and clinical findings, population statistics, and policy decisions. The reported rates of prevalence for developmental disabilities published by different US federal agencies have ranged widely from 3% to 17%. This represents a 5-fold difference. Equally confusing is the inconsistent and ambiguous adoption of initialisms. These initialisms include ID/DD, IDD, and I/DD for which it is not always clear if these initialisms reference separate and independent populations (eg, ID or DD) or populations with co-occurring conditions (eg, persons with ID and DD). This Narrative Review discusses these issues and proposed a number of recommendations that would contribute to enhanced consistency and clarity of understanding for stakeholders, administrators, practitioners, researchers, and policy makers.
Conclusion: Authors of scholarly works, clinical publications, policies, and position papers are encouraged to provide a clear operational definition as well as the choice of initialisms used (eg, ID/DD, IDD, I/DD, etc) when it is first used.