Autism spectrum disorder (ASD) is a condition that affects the development of social and communication skills. It includes features of four conditions which were once thought to be separate syndromes - autistic disorder, Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder. Signs and symptoms often become apparent in the first 2-3 years of life and vary significantly from person to person. Common symptoms shared by people with ASD include restrictive and repetitive behaviors, social impairment and communication difficulties. The underlying cause of ASD is generally unknown and it is likely that a variety of factors contribute to the development of the condition. ASD appears to run in some families, suggesting that genetics may play a role in some cases. Although there is no cure for ASD, treatment is available that significantly improves the long-term outlook for affected people. Treatment often includes a combination of techniques such as medications, occupational therapy, speech therapy and physical therapy.
The underlying cause of autism spectrum disorder (ASD) is generally unknown. Scientists suspect that it is a multifactorial condition, meaning that a variety of factors (both genetic and environmental) likely contribute to the development of the condition.
Having older parents (a mother who is 35 or older, and/or a father who is 40 or older when the baby is born)
Having certain genetic conditions (including Down syndrome, fragile X syndrome, and tuberous sclerosis)
Exposure to certain prescriptive medications during pregnancy (such as valproic acid, thalidomide)
Of note, no scientific evidence for a relationship between vaccines and autism has been identified.
Last updated: 12/2/2016
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.
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.
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.
Last updated: 10/19/2011
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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.