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doi: 10.1097/01.NNN.0000279068.10004.f0
Department: the Waiting Room: By the Numbers

Autism spectrum disorders (ASDs) are developmental disabilities. People with ASDs can have difficulty initiating social interactions, understanding other people's feelings or talking about their own, and adapting to changes in routine. The cognitive abilities of people with ASDs can range from severely challenged to gifted. Some children diagnosed with these disorders remain mute throughout their lives; others develop language as late as age 9.

1 in 150:

The estimated number of children born with an ASD, according to the Autism Society of America and based on 2007 data from the Centers for Disease Control and Prevention. Although the number has risen over the past decade, it's unclear whether this is due to a change in the way the condition is diagnosed or to a true increase in cases. Some groups interpret the CDC data differently and think the prevalence is lower. The rate of ASDs is lower than the rate of mental retardation but higher than the rates of cerebral palsy, hearing loss, and vision impairment.

4 to 1:

Number of boys who develop autism spectrum disorders, compared to the number of girls.


Percentage of children with ASDs diagnosed between 4 and 5 years of age. Most children with ASDs have documented developmental concerns before reaching age 3.

1 in 4:

Number of children with an ASD who develop seizures, which usually start in early childhood or adolescence.


Percentage of the time an identical twin will have an ASD if the other twin has autism.


Percentage of the time a non-identical twin will have an ASD if the other twin has autism.


Percent chance of having a second child with an ASD if you have already had one child with autism.

Source: National Center on Birth Defects and Developmental Disabilities (; CDC Feb. 9 report, the first summary of prevalence data on autism spectrum disorders in the U.S.

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