What causes autism?

Autism spectrum disorder is a developmental condition that begins during early brain development, before birth or in early infancy. Although autism does not have a single known cause, research suggests that both genetic and environmental factors may increase the likelihood of a child developing autism.

It is completely normal, especially right after a diagnosis, to wonder what caused your child’s autism or to question past decisions. Parents often feel shocked, worried, guilty, or even relieved to finally have a name for what they’ve been seeing. Whatever you are feeling right now is valid.

Here are some factors that have been associated with an increased likelihood of autism:

• Having a sibling with autism
  
• Being born to older parents
  
• Certain genetic conditions, such as fragile X syndrome
  
• Very low birth weight
  
• Complications during pregnancy or birth
  

Other factors that research has linked with a higher likelihood of autism include extreme prematurity, certain prenatal exposures (such as significant air pollution or some pesticides), and some maternal health conditions during pregnancy, like obesity, diabetes, or immune system disorders.  These are risk factors, not guarantees, and many children with autism do not have any of them.

Extensive research has found no link between vaccines and autism. Decades of studies around the world show that routine childhood vaccines, including vaccines that contain thimerosal or aluminum, do not cause autism.

Most importantly, nothing a parent did—or did not do—during pregnancy or early childhood has been shown to cause autism. While certain risk factors may be present, parents are not to blame, and many children with autism have no clear identifiable risk factors at all.

Autism is relatively common, affecting about 1 in 36 children, and it reflects differences in how the brain develops and processes information. You can best help your child by learning about the condition, building on their strengths, and connecting with support and services.