The Prevalence and Sociodemographic Characteristics of Intellectual Disability with Co-Occurring Attention-Deficit/Hyperactivity Disorder and Learning Disability.

Population-based estimates of intellectual disability (ID) and its co-occurrence with other neurodevelopmental disorders remain limited in the United States. Using data from the National Survey of Children's Health and the National Health Interview Survey (2021-2023), this study provides updated national estimates about the lifetime prevalence and sociodemographic characteristics of ID, with and without co-occurring attention-deficit/ hyperactivity disorder (ADHD) and learning disability (LD), among U.S. children ages 6-17 years. Across surveys, results revealed that lifetime prevalence of ID ranges from approximately 1.5% to 2.0% and that ID rarely occurs without ADHD and LD. As hypothesized, prevalence patterns varied significantly across sociodemographic groups, with higher rates among older children, males, non-Hispanic children, and children from lower-income families. We found high overlap between ID and LD in both surveys. Given that these conditions are considered mutually exclusive in federal education law, this high overlap raises questions about the validity of the ID and LD items in both surveys. Strengthening measurement of these and other conditions in national surveys will help ensure more accurate estimates of population needs and inform more effective education and health policy.