What causes IDDs?

Intellectual and developmental disabilities (IDDs) have a variety of causes. Some possible causes include (but are not limited to):1,2,3

  • Genetic mutations, additions, or deletions: for example, most cases of Rett syndrome are caused by a change in the Methly-CpG-binding Protein 2 (MECP2) gene
  • Chromosome abnormalities, such as an extra chromosome or a missing chromosome: for example, Down syndrome [link to topic] results from having an extra copy or part of a copy of chromosome 21
  • Exposure to certain substances while in the womb: for example, exposure to alcohol while in the womb can result in fetal alcohol spectrum disorder
  • Infections during pregnancy: for example, infants whose mothers had cytomegalovirus during pregnancy may have hearing, vision, and neurological problems
  • Problems during childbirth: for example, an umbilical cord that gets wrapped around a baby’s neck during delivery could cut off the supply of blood and oxygen to the brain resulting in IDDs
  • Traumatic Brain Injury (TBI)
  • Preterm birth


  1. American Academy of Pediatrics. (July 30, 2012). Health issues: Outlook for children with intellectual disabilities. Retrieved August 9, 2012, from http://www.healthychildren.org/English/health-issues/conditions/developmental-disabilities/Pages/Outlook-for-Children-with-Intellectual-Disabilities.aspx External Web Site Policy
  2. National Dissemination Center for Children with Disabilities (NICHCY). (January, 2011). NICHCY disability fact sheet #8: Intellectual disabilities. Retrieved August 9, 2012, from https://www.parentcenterhub.org/intellectual/ External Web Site Policy [PDF for Factsheet #8: http://nichcy.org/wp-content/uploads/docs/fs8.pdf External Web Site Policy (PDF - 123 KB)]
  3. American Academy of Pediatrics. (July 30, 2012). Health issues: Intellectual disability. Retrieved August 9, 2012, from http://www.healthychildren.org/English/health-issues/conditions/developmental-disabilities/Pages/Intellectual-Disability.aspx External Web Site Policy

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