Autism Spectrum Disorder (ASD) FAQs

Do vaccines cause autism spectrum disorders (ASDs)?

Many studies that have looked at whether there is a relationship between vaccines and autism spectrum disorders (ASDs). To date, the studies continue to show that vaccines are not associated with ASDs.

However, CDC knows that some parents and others still have concerns. To address these concerns, CDC is part of the Inter-Agency Autism Coordinating Committee (IACC), which is working with the National Vaccine Advisory Committee (NVAC) on this issue. The job of the NVAC is to advise and make recommendations regarding the National Vaccine Program. Communication between the IACC and NVAC will allow each group to share skills and knowledge, improve coordination, and promote better use of research resources on vaccine topics.

Is there an ASD epidemic?

More people than ever before are being diagnosed with an ASD. It is unclear exactly how much of this increase is due to a broader definition of ASDs and better efforts in diagnosis. However, a true increase in the number of people with an ASD cannot be ruled out. We believe the increase in the diagnosis of ASDs is likely due to a combination of these factors.

CDC is working with partners to study the prevalence of ASDs over time, so that we can find out if the number of children with these disorders is rising, dropping, or staying the same.

We do know that ASDs are more common than we thought before and should be considered an urgent public health concern.

There is still a lot to learn about ASDs. In addition, increased concern in the communities, continued demand for services, and reports estimating a prevalence of about 1 percent show the need for a coordinated and serious national response to improve the lives of people with ASDs.

Can adults be diagnosed with an ASD?

Yes, adults can be diagnosed with an ASD. Diagnosis includes looking at the person's medical history, watching the person's behavior, and giving the person some psychological tests. But, it can be more challenging to diagnose an adult because it is not always possible to know about the person's development during the first few years of life, and a long history of other diagnoses may complicate an ASD diagnosis. Because the focus of ASDs has been on children, we still have much to learn about the prevalence and causes of ASDs across the lifespan. Behavioral interventions can be effective for adults coping with a new diagnosis of autism.

How many children with ASDs are being served through public special education programs?

In 2007, 258,305 children 6 through 21 years of age and 39,434 children 3 through 5 years of age were served under the "autism" classification for special education services. Not all children with an ASD receive special education services under the classification of "autism," so the education data are not meant to represent the actual number of people with an ASD.

Has the number of children being served under an ASD classification in public special education programs changed?

Yes. between1998 to 2007, the number of 6 to 21 year old children receiving services for an ASD in public special education programs increased from 54,064 to 258,305. While it is clear that more children are getting special education services for ASDs than ever before, it is important to remember that this classification was only added in the early 1990s. Growth in the number of children classified may be caused in part by the addition of autism as a special education category.


Autism is a developmental disability. See Answer

How do the rates of ASDs in special education compare with those of other special education categories?

In 2007, according to Individuals with Disabilities Education Act administrative counts, 5,912,586 children 6 through 21 years of age received services through 13 categories in public special education programs. "Specific learning disability" was the most frequent education category identified, followed by "speech and language impairment." Together, these two categories made up nearly 64% of all special education placements. The intellectual disability classification accounted for about 8% (487,854). Autism accounted for about 4% (256,863).

CDC's Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) found the autism rate among 8-year-old children in 2000 to be 6.5 per 1,000. That's lower than the rate for intellectual disability/mental retardation (12.0 per 1,000) but higher than the rate for cerebral palsy (3.1 per 1,000), hearing loss (1.2 per 1,000), and vision impairment (1.2 per 1,000) found among children of the same age.

What are mitochondrial diseases?

Mitochondria are tiny parts of almost every cell in your body. Mitochondria are like the power house of the cells. They turn sugar and oxygen into energy that the cells need to work. In mitochondrial diseases, the mitochondria cannot efficiently turn sugar and oxygen into energy, so the cells do not work the way they should.

There are many types of mitochondrial disease, and they can affect different parts of the body: the brain, kidneys, muscles, heart, eyes, ears, and others. Mitochondrial diseases can affect one part of the body or many parts. The effects can be mild or very serious.

Not everyone with a mitochondrial disease will show symptoms. However, among the mitochondrial diseases that tend to affect children, symptoms usually appear in the toddler and preschool years.

Is there a link between mitochondrial diseases and ASDs?

A child with an ASD may or may not have a mitochondrial disease. When children have both an ASD and a mitochondrial disease, they sometimes have other problems too, including epilepsy, problems with muscle tone, or movement disorders.

More research is needed to find out how common it is for people to have an ASD and a mitochondrial disease. Right now, it seems rare. In general, more research about mitochondrial disease and ASDs is needed.


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Centers for Disease Control (CDC). "Autism Spectrum Disorders (ASDs)." Division of Birth Defects, National Center on Birth Defects and Developmental Disabilities. 20 July 2011. <>.

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