Experimental Pain Research in Individuals with Intellectual Developmental Disorder: A Scoping Review.

Background: Individuals with intellectual developmental disorders (intellectual disability, ID) are disproportionally affected by conditions associated with pain, which can be under recognized and undertreated, particularly in those with communication impairment. Although certain genetic etiologies of ID are associated with altered nociception, the extent to which pain perception, nociceptive processing, and pain expression differ in this population remains unclear. Methods: We conducted a scoping review of investigations using psychophysical procedures, including quantitative sensory testing (QST), or standardized clinically indicated painful procedures, to examine nociceptive processing and pain-evoked responses. Although the review focused on responses to noxious stimuli, studies incorporating innocuous stimuli as control conditions were eligible. Results: Thirty-seven studies met inclusion criteria. Experimental pain research in individuals with ID was characterized by substantial heterogeneity in study populations, psychophysical paradigms, stimuli modalities, and outcome measures. Participants represented all age groups and multiple ID etiologies; however, individuals with severe to profound ID were underrepresented and were assessed predominantly using proxy-reported behavioral measures. Modified QST protocols were generally feasible. Collectively, the evidence suggests that responses to noxious stimuli in individuals with ID are not uniformly diminished and may be atypical relative to typically developing controls. Behavioral, autonomic, and neurophysiological responses varied across studies and appeared to be influenced by underlying ID etiology. Conclusion: Experimental pain research in individuals with ID is feasible using modified QST paradigms and standardized clinical procedures; however, individuals with severe to profound ID remain underrepresented. Methodological heterogeneity, inconsistent reporting, and limited validation of outcome measures constrain interpretation of nociceptive processing and cross-study comparability. These findings highlight important gaps in the evidence supporting pain assessment in individuals with ID. Future research should prioritize development and validation of ID-specific pain assessment tools and inclusion of individuals across the full spectrum of ID severity to improve understanding of nociceptive processing and support evidence-informed pain management.