What causes Autism?

What causes Autism?

An overview of autism spectrum disorders and the role of genetic testing in children and embryos.

Written by Maria Katz, MS, CGC, Reviewed by Xiaoli Du, PhD, FACMG, DABMGG, CGC,CGMBS

Dr. Du is an American Board of Medical Genetics and Genomics (ABMGG) certified geneticist. With a passion for precision medicine, she leverages cutting-edge molecular genetics and cytogenetics technology to improve outcomes for individuals affected by genetic conditions. Dr. Du has nine years of clinical genetic diagnosis experience in both the public and private sectors.

What causes Autism?

This is not a simple answer, as Autism Spectrum Disorders themselves are complex. Autism Spectrum Disorders are not a single diagnosis but are used to describe a subset of common signs and symptoms relating to differences in language, socialization and repetitive behavior1. The CDC reports that one in forty-four children in the U.S. are diagnosed with an Autism Spectrum Disorder, impacting individuals of all ethnic and socioeconomic backgrounds3.

It is well established that genetics can contribute to Autism Spectrum Disorders. Over 20-30% of diagnosed Autism Spectrum Disorder cases can be  attributed to an underlying genetic cause2,5,6,8-14. In the remaining individuals with Autism for which an underlying genetic cause cannot be identified, the cause is considered to be multifactorial. Multifactorial means a combination of multiple genetic and environmental factors that contribute together.

Is there genetic testing for Autism?

Yes. Multiple testing options are available for Autism Spectrum Disorders. There is no one single test that can identify every cause of Autism.

In the American College of Medical Genetics (ACMG) 2013 guidelines for genetic testing for Autism Spectrum Disorders, the recommended testing discussed is an evaluation of chromosomes (known as karyotype testing), an evaluation for extra and missing pieces of chromosomes (chromosome microarray analysis) and single gene testing for genes commonly associated with Autism Spectrum Disorders. Since 2013, genetic testing has been moving towards looking across all the letters that make up our genome (exome or whole-genome sequencing)12

Many laboratories across the United States, including Blueprint Genetics, Fulgent and Prevention Genetics, offer Autism Spectrum Disorder gene panels for children or adults.
Gene panels can look at changes in more than one gene at one time.

Can I test my embryo for Autism? How accurate is embryo testing for Autism?

Yes, only through Orchid's whole genome embryo screening (PGT-WGS).

Orchid's embryo screening looks for a specific set of genes that have been identified by a group of expert geneticists (clinical domain group) as being linked to Autism Spectrum Disorders and other neurodevelopmental disorders4.

There are a few ways to think about the accuracy of a test. Let's start with this pie graph. Orchid can only screen for known genetic causes of Autism Spectrum Disorders (the light blue), therefore there is a large proportion of Autism Spectrum Disorder cases that Orchid cannot account for.

Within the category of Genetic Autism Spectrum Disorders, Orchids testing is highly accurate. This means that if an embryo were to test positive, it would be affected by the condition it tested positive for. 

It is important to remember that while embryo screening is very accurate, it is still a screening test. The test is performed on cells that will eventually become the placenta, and not on the fetus itself. Additionally, no test can detect all possible genetic causes of Autism, and not all Autism cases are caused by a change in a single gene.

What are the benefits of genetic testing for Autism?

For an individual with a clinical Autism Spectrum Disorders diagnosis, genetic testing for autism can:

  • Assist with a diagnosis.
  • Some genetic Autism Spectrum Disorders can be associated with other health concerns. Early identification can allow for screening for other possible health issues. 
  • Personalized treatment management of symptoms based on a genetic diagnosis.
  • Provide recurrence chance information for family members. Assist in family planning.
  • Connect individuals with appropriate resources & support.

For a family looking to screen an embryo for autism:

  • Provide information about genetic Autism Spectrum Disorders  in an embryo and help families make informed decisions. 
  • Reduce the chances of future offspring being affected with a genetic Autism Spectrum Disorders.

What are the limitations of genetic testing for Autism?

Some limitation for an individual with a clinical Autism Spectrum Disorders diagnosis:

  • Access to genetic testing and genetic counseling may be limited in rural areas.
  • Insurance may not cover the cost of the genetic testing which may be expensive.
  • Autism Spectrum Disorders are complex and some results may be complicated to interpret or understand. 
  • The results of genetic testing are considered protected health information and are confidential to the extent allowed by state and federal law. However there are federal laws in place that prohibit health insurers and employers from discriminating based on genetic information (for example, the Genetic Information Nondiscrimination Act (GINA) of 2008 (Public Law 110-233)). But there are currently no federal laws that prohibit life insurance, long term care, or disability insurance companies from discriminating based on genetic information. Individual states may have more comprehensive laws in this area.

Some limitations of embryo screening for autism:

  • There is no single test that can identify all possible genetic causes for Autism Spectrum Disorders, and not all Autism Spectrum Disorders are due to a single change in an individual's chromosomes or genes, negative results may be falsely reassuring for parents.
  • Some genetic results are complex and complicated to understand, some parents may have uncertainty of what to do with the results of testing.

  1. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Arlington, VA: American Psychiatric Association, 2013
  2. Buja A, Volfovsky N, Krieger AM, Lord C, Lash AE, Wigler M, et al. Damaging de novo mutations diminish motor skills in children on the autism spectrum. Proc Natl Acad Sci (2018) 115(8):E1859–66. 10.1073/pnas.171542711C
  3. Center for Disease Control and Prevention. (2015, August). Autism spectrum disorder (ASD). Retrieved from http://www.cdc.gov/ncbddd/autism/index.html.
  4. Clinical Domain Working Groups. Intellectual Disability and Autism Gene Curation Expert Panel. Retrieved from: https://www.clinicalgenome.org/affiliation/40006/
  5. Greshwind, 2011. Genetics of Autism Spectrum Disorders
  6. Miller, D. T., Adam, M. P., Aradhya, S., Biesecker, L. G., Brothman, A. R., Carter, N. P., Church, D. M., Crolla, J. A., Eichler, E. E., Epstein, C. J., Faucett, W. A., Feuk, L., Friedman, J. M., Hamosh, A., Jackson, L., Kaminsky, E. B., Kok, K., Krantz, I. D., Kuhn, R. M., Lee, C., … Ledbetter, D. H. (2010). Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. American journal of human genetics, 86(5), 749–764. https://doi.org/10.1016/j.ajhg.2010.04.006
  7. Morris-Rosendahl, D. J., & Crocq, M. A. (2020). Neurodevelopmental disorders-the history and future of a diagnostic concept. Dialogues in clinical neuroscience, 22(1), 65–72.
  8. National Institute for Mental Health. (n.d.) Autism spectrum disorder. Retrieved from http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-asd/index.shtml.
  9. Ronemus M, Iossifov I, Levy D, Wigler M. The role of de novo mutations in the genetics of autism spectrum disorders. Nat Rev Genet 2014; 15: 133–41. 
  10. Scherer,S, & Woodbury-Smith, M. 2018. Progress in the genetics of Autism spectrum disorder.
  11. Schaefer, G. B., Mendelsohn, N. J., & Professional Practice and Guidelines Committee (2013). Clinical genetics evaluation in identifying the etiology of autism spectrum disorders: 2013 guideline revisions. Genetics in medicine : official journal of the American College of Medical Genetics, 15(5), 399–407. https://doi.org/10.1038/gim.2013.32
  12. Srivastava, S., Love-Nichols, J. A., Dies, K. A., Ledbetter, D. H., Martin, C. L., Chung, W. K., Firth, H. V., Frazier, T., Hansen, R. L., Prock, L., Brunner, H., Hoang, N., Scherer, S. W., Sahin, M., Miller, D. T., & NDD Exome Scoping Review Work Group (2019). Meta-analysis and multidisciplinary consensus statement: exome sequencing is a first-tier clinical diagnostic test for individuals with neurodevelopmental disorders. Genetics in medicine : official journal of the American College of Medical Genetics, 21(11), 2413–2421. https://doi.org/10.1038/s41436-019-0554-6
  13. Stefanski et. al. Clinical sequencing yield in epilepsy, autism spectrum disorder, and intellectual disability: A systematic review and meta-analysis. Epilepsia. 2021; 62: 143–151. PMID: 33200402
  14. Woodbury-Smith, M., & Scherer, S. W. (2018). Progress in the genetics of autism spectrum disorder. Developmental medicine and child neurology, 60(5), 445–451. https://doi.org/10.1111/dmcn.13717
  15. Yoon et. al. Rates of contributory de novo mutation in high and low-risk autism families. Commun. Biol. 2021; 4: 1026. PMID: 34471188

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