At a glance
Answers to frequently asked questions (FAQs) about autism spectrum disorder (ASD).
FAQs about ASD
Q: Do vaccines cause autism spectrum disorder (ASD)?
A: Many studies have looked at whether there is a relationship between vaccines and ASD. To date, the studies continue to show that vaccines are not associated with ASD.
CDC knows 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 the NVAC will allow each group to share skills and knowledge, improve coordination, and promote better use of research resources on vaccine topics.
For more information about vaccines and ASD, see the following sites:
Immunization Safety Office | CDC
- Thimerosal and Vaccines
- Measles, Mumps, Rubella (MMR) Vaccine
- Thimerosal in Flu Vaccine
- Timeline: Thimerosal in Vaccines (1999–2010)
- Autism and Vaccines
Q: Are more children being diagnosed with ASD?
A: CDC is working with partners to study the prevalence of ASD over time so we can find out if the number of children with ASD is rising, dropping, or staying the same.
The prevalence of ASD among 8-year-olds has increased most years since CDC began tracking ASD in 2000. Prevalence estimates also vary across different communities. Increases between years and differences across sites within a year are likely due to a combination of factors including diagnostic practices and access to services in communities. Equitable and early identification of ASD is a public health priority so children with ASD can receive services they may need to achieve their full potential.
Q: Can adults be diagnosed with ASD?
A: Yes, adults can be diagnosed with 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 ASD research has been on children, we still have much to learn about the prevalence and causes of ASD across the lifespan. Behavioral interventions can be effective for adults coping with a new diagnosis of autism.
Q: What are mitochondrial diseases or disorders?
A: 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 correctly.
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 can affect many parts. They can affect those parts mildly or very seriously.
Not everyone with a mitochondrial disease will show symptoms. However, when discussing the group of mitochondrial diseases that tend to affect children, symptoms usually appear in the toddler and preschool years.
Mitochondrial diseases and disorders are the same thing.
Q: Is there a relationship between mitochondrial disease and autism?
A: A child with a mitochondrial disease
- May also have an autism spectrum disorder,
- May have some of the symptoms or signs of autism, or
- May not have any signs or symptoms related to autism.
A child with autism may or may not have a mitochondrial disease. When a child has both autism and a mitochondrial disease, they sometimes have other problems as well, including epilepsy, problems with muscle tone, and/or movement disorders.
More research is needed to find out how common it is for people to have autism and a mitochondrial disorder. Right now, it seems rare. In general, more research about mitochondrial disease and autism is needed.
Q: What is regressive encephalopathy?
A: Encephalopathy is a medical term for a disease or disorder of the brain. It usually means a slowing down of brain function. Regression happens when a person loses skills that they used to have, such as walking or talking or even being social.
Regressive encephalopathy means there is a disease or disorder in the brain that makes a person lose skills they once had.
We know that sometimes children with mitochondrial diseases seem to be developing as they should, but around toddler or preschool age, they regress. The disease was there all the time, but something happens that "sets it off." This could be something like malnutrition, an illness such as flu, a high fever, or dehydration, or it could be something else.
Q: Is there a relationship between autism and encephalopathy?
A: Most children with an autism spectrum disorder do not have and have not had an encephalopathy. Some children with an autism spectrum disorder have had regression and some have had a regressive encephalopathy.
Q: What do we know about the relationship between mitochondrial disease and other disorders related to the brain?
A: Different parts of the brain have different functions. The area of the brain that is damaged by a mitochondrial disease determines how the person is impacted. This means that a person could have seizures, trouble talking or interacting with people, difficulty eating, muscle weakness, or other problems. They could have one issue or several.
Q: Do vaccines cause or worsen mitochondrial diseases?
A: As of now, there are no scientific studies that say vaccines cause or worsen mitochondrial diseases. We do know certain illnesses that can be prevented by vaccines, such as the flu, can trigger the regression that is related to a mitochondrial disease. More research is needed to determine if there are rare cases where underlying mitochondrial disorders are triggered by anything related to vaccines. However, we know that for most children, vaccines are a safe and important way to prevent life-threatening diseases.
Q: Are all children routinely tested for mitochondrial diseases? What about children with autism?
A: Children are not routinely tested for mitochondrial diseases. This includes children with autism and other developmental delays.
Testing is not easy and may involve taking multiple samples of blood, and often samples of muscle. Doctors decide whether testing for mitochondrial diseases should be done based on a child's signs and symptoms.
Q: Should I have my child tested for a mitochondrial disease?
A: If you are worried that your child might have a mitochondrial disease, talk to your child's doctor.