What causes autism?

There are many causes of autism.

Research suggests that autism spectrum disorder (ASD) develops from a combination of:

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.

Word cloud with some of the factors that influence ASD

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?

Vaccines do not cause autism. It is possible that the timing of an autism diagnosis might coincide with the recommended vaccine schedule for children and adolescents. But scientists have conducted extensive research over the last two decades to determine there is no link between childhood vaccinations and autism. The results of this research is clear: Vaccines do not cause autism. Additionally, vaccination can protect children from many preventable diseases like measles.

The American Academy of Pediatrics has compiled a comprehensive list of this research.

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 for 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

Contact the Autism Response Team

Autism Speaks' Autism Response Team can help you with information, resources and opportunities.

The information above is not meant to diagnose or treat. It should not take the place of consultation with a qualified health care professional.