What causes autism?
There are many causes of autism. Research suggests that autism spectrum disorder (ASD) develops from a combination of:
- Genetic influences and
- Environmental influences, including social determinants
These factors appear to increase the risk of autism and shape the type of autism that a child will develop. However, it’s important to keep in mind that increased risk is not the same as a cause. For example, some gene changes associated with autism can also be found in people who don’t have the disorder. Similarly, not everyone exposed to an environmental risk factor for autism will develop the disorder. In fact, most will not.
Autism risk factors
How do genetic and environmental influences give rise to autism?
Most appear to affect crucial aspects of early brain development. Many autism risk genes influence other networks of genes, increasing or decreasing their expression. Some appear to affect how brain nerve cells, or neurons, communicate with each other. Others appear to affect how entire regions of the brain communicate with each other. Research continues to explore these differences with an eye to developing interventions and supports that can improve quality of life.
Do vaccines cause autism?
There is no connection between vaccines and autism. Autism is often diagnosed around the same time children receive routine vaccinations, which has led to concerns about a connection—but decades of scientific research have confirmed that vaccines do not cause autism. In fact, vaccines play a crucial role in protecting children from serious diseases like measles. Explore the research on vaccines and autism.
Is autism genetic?
Research tells us that autism tends to run in families, and a meta-analysis of 7 twin studies claim that 60 to 90% of the risk of autism comes from your genome. If you have a child with autism, you are more likely to have another autistic child. Your other family members are also more likely to have a child with ASD.
Changes in certain genes or your genome increase the risk that a child will develop autism. If a parent carries one or more of these gene changes, they may get passed to a child (even if the parent does not have autism). For some people, a high risk for ASD can be associated with a genetic disorder, such as Rett syndrome or fragile X syndrome. For the majority of autism, multiple changes in other regions of your DNA increase the risk of autism spectrum disorder. The majority of these DNA changes do not cause autism by themselves but work in conjunction with many other genes and environmental factors to cause autism.
If you or your child has ASD, we recommend that you explore genetic testing. Genetic testing could show you the genetic cause of you or your child’s autism and reveal any genetic mutations that might be linked to serious co-occurring conditions like epilepsy. Genetic testing can give doctors useful information so they can provide better, more personalized interventions. Read two family's stories on how genomics help their understanding of autism and receiving personalized healthcare.
What environmental factors are associated with autism?
According to the National Institute of Environmental Health Sciences, certain environmental influences may increase autism risk:
- Advanced parental age
- Prenatal exposure to air pollution or certain pesticides
- Maternal obesity, diabetes or immune system disorders
- Extreme prematurity or very low birth weight
- Birth complications leading to periods of oxygen deprivation to the baby’s brain
Why is autism on the rise?
Autism prevalence has risen due to increased awareness of autism, broader diagnostic criteria for autism, improved screening tools and standardized screening processes. These factors have led to earlier detection and more diagnoses.
- Changes in diagnostic criteria: Diagnostic guidelines have evolved from the DSM-III to the current DSM-5, broadening the definition of autism. The modern autism diagnosis now includes people with lower support needs who previously got a different diagnosis or were overlooked entirely.
- Improved screening tools and procedures: The development and widespread use of more effective screening tools, such as the Modified Checklist for Autism in Toddlers (M-CHAT) published in 2001, have enabled earlier and more accurate identification of autism in all young children.
- Increased awareness: Greater autism awareness in the public as well as among medical professionals has led to an increase in diagnoses. In 2007, the American Academy of Pediatrics (AAP) formally recommended that pediatricians begin incorporating standardized autism screening at 18- and 24-month well-child visits, leading to a rise in autism diagnosis and improved access to early intervention.
While the impact of other genetic and environmental factors on prevalence is still being studied, they likely account for only a small part of the increase.
Contact the Autism Response Team
Autism Speaks' Autism Response Team can help you with information, resources and opportunities.
- In English: 888-288-4762 | help@autismspeaks.org
- En Español: 888-772-9050 | ayuda@autismspeaks.org
The information above is not meant to diagnose or treat. It should not take the place of consultation with a qualified health care professional.