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An Initiative of National Trust
for the Welfare of Persons with Autism, Cerebral Palsy,
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What causes Autism?

There are many medical diseases or conditions that can cause Autism. These include genetic conditions such as Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis, Phenylketonuria and Rett syndrome , besides a number of other chromosomal disorders. The non-genetic insults to maturation and development of brain such as certain infections in early pregnancy (for example rubella infection), the prenatal exposure to harmful medicines and chemicals and damage to brain around the time of birth also are known to cause Autism.

However, all these causes put together are found in only a small number of persons with Autism. In other words, a specific medical cause can be identified only in the minority of persons with Autism, and no specific single cause is identifiable in the majority of persons with Autism. In general, research done in Autism in the last 2 decades has shown that genetic factors play an important role in the causation of Autism. A number of “risk genes” have been identified. It is possible that when many such risk genes come together in a given child, it may lead to the development of Autism. These risk genes probably have an adverse or harmful effect on brain maturation and development. But the exact role of these genetic factors is still being explored.

Research has also shown that environmental factors also could play an important role, and that these 2 factors – genetic and environmental – could interact with each other. In other words Autism could develop because of a combination of harmful genetic and environmental factors. One important preventable environmental factor is lack of adequate social stimulation in infancy.

It is important to note that not all genetic causes are hereditary or inherited. Genetic problems can arise without any family history.

Very active research is being conducted all over the world on the changes in structure and function of the brain in individuals with Autism. A number of subtle structural and functional alterations in the brain have been noted. It is still not entirely clear what these changes mean and how are they are related to the manifestations of Autism. One theory that is gaining some support is that there is disturbance in the connectivity between different structures of the brain, leading to disturbed networks and circuitries that are responsible for social and language development.

Glossary:

Fragile X Syndrome is a genetic condition that causes a range of developmental problems including Autism.

Angelman syndrome is a complex genetic disorder that primarily affects the nervous system.

Tuberous sclerosis is a rare genetic disease that causes benign tumors to grow in the brain and other organs.

Phenylketonuria is an inherited disorder that increases the levels of a substance called phenylalanine in the blood. Phenylalanine is a building block of proteins.

Rett syndrome is a brain disorder that occurs almost exclusively in girls.

Rubella infection also known as German measles or three-day measles is a disease caused by the rubella virus.

References

  • Elsabbagh M, Divan G, Koh YJ, Kim YS, Kauchali S, Marcin C, et al. Global prevalence of autism and other pervasive developmental disorders. Autism Res. 2012 Jun;5(3):160-79.
  • Levy SE, Mandell DS, Schultz RT. Autism. Lancet. 2009 Nov 7;374(9701):1627-38.
  • Betancur C. Etiological heterogeneity in autism spectrum disorders: more than 100 genetic and genomic disorders and still counting. Brain Res. 2011 Mar 22;1380:42-77.
  • Pelphrey KA, Shultz S, Hudac CM, Vander Wyk BC. Research review: Constraining heterogeneity: the social brain and its development in autism spectrum disorder. J Child Psychol Psychiatry. 2011 Jun;52(6):631-44.
  • Fernell E, Eriksson MA, Gillberg C. Early diagnosis of autism and impact on prognosis: a narrative review. Clin Epidemiol. 2013;5:33-43.
  • Rutter, M., Kreppner, J., Croft, C., Murin, M., Colvert, E., Beckett, C., Castle, J. and Sonuga-Barke, E. (2007), Early adolescent outcomes of institutionally deprived and non-deprived adoptees. III. Quasi-autism. Journal of Child Psychology and Psychiatry, 48: 1200–1207.
  • Hoksbergen R, ter Laak J, Rijk K, van Dijkum C, Stoutjesdijk F. Post-Institutional Autistic Syndrome in Romanian adoptees. J Autism Dev Disord. 2005 Oct;35(5):615-23.
  • Wan MW, Green J, Elsabbagh M, Johnson M, Charman T, Plummer F; BASIS Team. Quality of interaction between at-risk infants and caregiver at 12-15 months is associated with 3-year autism outcome. J Child Psychol Psychiatry. 2013 Jul;54(7):763-71.
  • Fein D, Barton M, Eigsti IM, Kelley E, Naigles L, Schultz RT, Stevens M, Helt M, Orinstein A, Rosenthal M, Troyb E, Tyson K. Optimal outcome in individuals with a history of autism. J Child Psychol Psychiatry. 2013 Feb;54(2):195-20
  • Genetic Home Reference http://ghr.nlm.nih.gov/ (for Glossary)
  
 
  Autism Spectrum Disorders or ASD is commonly called Autism Neuro- typical: A term used for people who do not have Autism or ASD  
 
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