Types and Diagnosis of Childhood Intellectual Disabilities: Advancing Accuracy for Better Outcomes

Intellectual disability (ID)-termed intellectual developmental disorder in DSM-5-TR and disorders of intellectual development in ICD-11-is a heterogeneous spectrum of neurodevelopmental conditions characterized by impairments in general intellectual abilities and adaptive functioning, with onset during the developmental period. Precise and early recognition of ID can alter developmental trajectories by clarifying prognosis, guiding targeted genetic and medical investigations, initiating time-sensitive interventions, preventing diagnostic overshadowing, and informing educational planning and family counseling. This narrative review synthesizes contemporary diagnostic standards from DSM-5-TR and ICD-11, recent updates in epidemiology, and an aetiology-oriented framework for classifying "types" of intellectual disability. It further outlines current best practices in diagnostic work-up-including developmental surveillance and screening, standardized cognitive and adaptive assessments, genomic testing (microarray, exome/genome sequencing, and syndrome-specific assays), selective metabolic studies, and neuroimaging or EEG when indicated. Additionally, the review explores culturally responsive and equitable assessment, special diagnostic contexts (such as profound impairment, sensory and motor confounds, and bilingualism), and the frequent co-occurrence of other neurodevelopmental and medical disorders. The discussion concludes with practical, stepwise diagnostic pathways that clinicians can readily apply and anticipates emerging frontiers-such as genomic medicine and digital phenotyping-that promise to enhance diagnostic yield and clinical utility in the near future.