Causes
The number of children diagnosed with autism spectrum disorder is rising. It's not clear whether this is due to better detection and reporting or a real increase in the number of cases, or both. Autism spectrum disorder affects children of all races and nationalities, but certain factors increase a child's risk.
Risk Factors
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Gender-related genes. It is still under debate, much research shows that boys are about four times more likely to develop autism spectrum disorder than girls are.
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Family history. Families who have one child with autism spectrum disorder have an increased risk of having another child with the disorder. It's also not uncommon for parents or relatives of a child with an autism spectrum disorder to have minor problems with social or communication skills themselves or to engage in certain behaviors typical of the disorder.
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Other disorders. Children with certain medical conditions have a higher than normal risk of autism spectrum disorder or autism-like symptoms. Examples include fragile X syndrome, an inherited disorder that causes intellectual problems; tuberous sclerosis, a condition in which benign tumors develop in the brain; and Rett syndrome, a genetic condition occurring almost exclusively in girls, which causes slowing of head growth, intellectual disability and loss of purposeful hand use.
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Extremely preterm babies. Babies born before 26 weeks of gestation may have a greater risk of autism spectrum disorder.
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Parents' ages. There may be a connection between children born to older parents and autism spectrum disorder, but more research is necessary to establish this link.
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​ Genetics
- ASD is a complex genetic disorder resulting from rare mutations and simultaneous genetic variations in multiple genes. Shared environmental experiences and epigenetic (non-genetic) factors may also be involved.
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- Nonautistic relatives of individuals with ASD display higher-than-normal rates of social, language, and cognitive deficits that are similar in quality to those found in ASD, but are less severe and not associated with intellectual deficits or epilepsy.
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- Neuropsychological impairments occur in many areas of functioning, including intelligence, attention, memory, language, and executive functions, due to structural abnormalities in the brain.
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- ASD is not represented by a localized abnormality in one part of the brain but rather by a lack of normal connectivity and communication among brain networks that underlie the core features of ASD.
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