Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.

Diseases

Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Autism spectrum disorders

*

* Not a rare disease

Other Names for this Disease

  • ASD
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

I would like information on autism.  I need to know if autism is something that you are born with and if it is genetic.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What are autism spectrum disorders (ASD)?

Autism spectrum disorders (ASD) are a group of developmental conditions characterized by social impairments, communication difficulties, and restricted, repetitive, and stereotyped patterns of behavior. Autistic disorder, sometimes called autism or classical ASD, is the most severe form of ASD, while other conditions along the spectrum include a milder form known as Asperger syndrome as well as childhood disintegrative disorder and pervasive developmental disorder not otherwise specified (PDD-NOS). Although ASD varies significantly in features and severity, it occurs worldwide and affects every age group.[1] Experts estimate that 1 out of 110 children will have an ASD.  Males are more likely to have an ASD than females.[2]
Last updated: 10/19/2011

Is autism something you are born with?

In approximately 10% of individuals, autism is associated with a genetic syndrome or a known chromosomal anomaly - most of which have additional recognizable features.  For example, autism can be associated with fragile X syndrome, tuberous sclerosis, the Smith-Lemli-Opitz syndrome, the Potocki-Lupski syndrome and additional chromosomal material on chromosome 15 associated with Prader-Willi and Angelman syndrome.[3]  These are conditions that people are born with.

The cause of autism is unknown (idiopathic) for 90% of individuals. However, children with autism are thought to be born with the disorder or born with the potential to develop it.  Some studies have noted, although very subtle, some signs of autism are detectable at eight months of age.  A number of behavioral symptoms of autism may be seen by 18 months of age such as: problems with eye contact, not responding to one’s name, joint attention problems, underdeveloped skills in pretend play and imitation, and problems with non-verbal communication and language.   But in general, the average age of autism diagnoses is three years old.[4]
Last updated: 12/8/2008

What causes autism spectrum disorders (ASD)?

There is no known single cause of autism spectrum disorders, but it is generally accepted that ASD is caused by abnormalities in brain structure or function. Brain scans often show differences in the shape and structure of the brain in children with ASD versus children without ASD. Researchers are investigating a number of theories, including the link between heredity, genetics, and medical problems. In many families, there appears to be a pattern of autism or related disabilities, further supporting a genetic basis to the disorder. While no one gene has been identified as causing ASD, researchers are searching for genetic material that children with ASD may have inherited. It also appears that some children are born with a susceptibility to ASD, but researchers have not yet identified a single "trigger" that causes autism to develop.[4]

Currently a genetic cause can be identified in 20% to 25% of children with ASD. The cause of autism in the remaining 75% to 80% remains unknown.[5]

A small number of cases can be traced to specific exposures during pregnancy. However, it remains unclear whether those who develop autism after such an exposure are also genetically predisposed to develop ASD. The search for other environmental causes of ASD has centered primarily on childhood immunizations given around the time that ASD is recognized; however, no scientific evidence for a relationship between vaccines and autism has been identified.[5]
Last updated: 10/19/2011

When the underlying cause of a person's autism spectrum disorder (ASD) cannot be found, could genetic factors still play a role?

Results of twin and family studies have shown that genetic factors play a role in about 90% of ASD cases. In most cases, however,  researchers do not believe that the cause of autism is due to just one gene. Rather, it is likely that variations in many genes along with various environmental factors interact during brain development to cause a susceptibility to autism. Although genes do play a role in autism, research has found that in families with one child with autism, the chance of having a second child with autism is about 20% or 1 in 5.[6] 

Researchers have identified a number of genes associated with autism. Studies of people with autism have found irregularities in several regions of the brain. Other studies suggest that people with autism have abnormal levels of serotonin or other neurotransmitters in the brain. These abnormalities suggest that autism could result from the disruption of normal brain development early in fetal development caused by defects in genes that control brain growth and that regulate how neurons communicate with each other.  While these findings are intriguing, they are preliminary and require further study.[1]

One study found a possible association between very small deletions (missing genetic material) or duplications (extra material) on the p arm of chromosome 16 in 1% of indiviudals with autism who had more than one family member affected. However, 99% of people with autism do not have this chromosome finding. Although more research is needed, this finding suggests that there may be another possible suseptibility gene for autism in this region of chromosome 16.[7]
Last updated: 10/19/2011

References
  • Autism Fact Sheet. National Institute of Neurological Disorders and Stroke. September 2011; http://www.ninds.nih.gov/disorders/autism/detail_autism.htm. Accessed 10/19/2011.
  • About Autism. Autism Society of America. http://www.autism-society.org/about-autism/. Accessed 10/19/2011.
  • Freitag CM. The genetics of autistic disorders and its clinical relevance: a review of the literature. Mol Psychiatry. 2007;
  • Causes. Autism Society of America. http://www.autism-society.org/about-autism/causes/. Accessed 10/19/2011.
  • Miles JH et al.. Autism Spectrum Disorders. GeneReviews. April 2010; http://www.ncbi.nlm.nih.gov/books/NBK1442/. Accessed 10/19/2011.
  • Ozonoff S, et al. Young GS, Carter A, Messinger D, Yirmiya N, Zwaigenbaum L, Bryson S, Carver LJ, Constantino JN, Dobkins K, Hutman T, Iverson JM, Landa R, Rogers SJ, Sigman M, Stone WL. Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study.. Pediatrics. 2011; [Epub ahead of print]:http://www.ncbi.nlm.nih.gov/pubmed/21844053. Accessed 10/19/2011.
  • Weiss L, Shen Y, Korn J, et.al.. Association between Microdeletion and Microduplication at 16p11.2 and Autism. New England Journal of Medicine (online). January 9, 2008;
Other Names for this Disease
  • ASD
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.