The Cause of IDD


Determine whether an assessment of cause has ever been done. If cause was established, consult available relevant management guidelines (eg, Health Watch Tables for specific syndromes).57,60,61

The cause of IDD is important to establish because it can inform preventive care, support, and treatment decisions.57-59

Refer for assessment

If cause is unknown, contact a genetics centre for advice on referring patients for an assessment or re-assessment.62,64-66


Advances surrounding genetic and environmental causes of IDD continue to increase the proportion of disorders with known origin. Clinical geneticists carry out assessment of cause and offer genetic counselling.62,63

Genetic Assessment: FAQ

The Genetic Assessment: Frequently Asked Questions fact sheet, developed by the Developmental Disabilities Primary Care Initiative at Surrey Place (Toronto, 2011) provides information on types of genetic assessments and referral procedures.

Genetics Centres in Canada

Contact information for Genetics Centres in Canada is available at the Canadian Association of Genetic Counsellors.

Health Watch Tables

Syndrome specific Health Watch Tables, developed by the Developmental Disabilities Primary Care Initiative at Surrey Place (Toronto, 2011) highlight health issues and preventive care actions for genetic syndromes such as Autism, Down Syndrome and Fetal Alcohol Syndrome Disorder.

  1. Cassidy SB, Allanson JE, editors. Management of Genetic Syndromes. 3rd ed. Hoboken, N.J.: Wiley-Blackwell; 2010.
  2. van Karnebeek CD, Houben RF, Lafek M, Giannasi W, Stockler S. The treatable intellectual disability APP [Website]  A digital tool to enhance diagnosis & care for rare diseases. Orphanet J Rare Dis. 2012;7:47.
  3. Srour M, Shevell M. Genetics and the investigation of developmental delay/intellectual disability. Arch Dis Child. 2014;99(4):386-9.
  4. Developmental Disabilities Primary Care Initiative. Health watch tables for specific syndromes. Surrey Place, Toronto, 2011-2014.
  5. Searle,Beverly: Website editor. Unique: Rare chromosome disorder support group [Website]. UK: Unique. 2017.
  6. Moeschler JB, Shevell M, Committee on Genetics. Comprehensive evaluation of the child with intellectual disability or global developmental delays. Pediatrics. 2014;134(3):e903-18.
  7. Boycott K, Hartley T, Adam S, Bernier F, Chong K, Fernandez BA, et al. The clinical application of genome-wide sequencing for monogenic diseases in Canada: Position statement of the Canadian college of medical geneticists. J Med Genet. 2015;52(7):431-7.
  8. Forster-Gibson C. Genetic assessment: Frequently asked questions. In: Sullivan WF, Developmental Disabilities Primary Care Initiative [DDPCI], editors. Tools for the primary care of people with developmental disabilities. Toronto: Surrey Place & MUMS Guideline Clearinghouse; 2011. p. 2-5.
  9. Provincial IODE Genetics Resource Centre, London Health Sciences Centre. Genetic resources Ontario [Website]. London, ON: London Health Sciences Centre. 2017.
  10. Adam,M. P., H. H. Ardinger, R. A. Pagon and S. E. Wallace.Gene reviews: Medical genetics information resource [Website]. Seattle: University of Washington. 1993-2017.
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