Prevalence of Autism Spectrum Disorders Among Children with Intellectual Disability


The study examined the prevalence, stability and characteristics pf ASD in children diagnosed with an intellectual disability.


The methodology used to assess the prevalence of ASD in children diagnoses with an intellectual disability identified 2,208 children through the South Carolina Autism and Developmental Disabilities Network. The data reviewed was done in threes phases including screening, extraction and case evaluation. The process included screening each child’s clinical  records, and public school information. Records were abstracted that included information on diagnoses, behavior descriptors and characteristics. The records were then evaluated for both an intellectual disability and autism status.


  • Rates of ASD in intellectual disabilities were substantially higher than ASD rates reported in the general U.S. population
  • Rates demonstrated elevated and increasing rates of ASD within diagnosis of an intellectual disability.
  • These efforts are warranted to reduce public health costs and support individual well-being for the approximately 24% of people with an intellectual disability who also meet the ASD criteria.


Tonnsen, B.L.; Boan, A.D.; Bradley, CC.; Charles, J.; Cohen, A.; Carpenter, L.A (2016). Prevalence of Autism Spectrum Disorders Among Children with Intellectual Disability. American Journal of Intellectual and Developmental Disabilities. 121 (6). 487-500