How common is autism?

Autism statistics from the U.S. Centers for Disease Control and Prevention (CDC) released in December 2021 identify around 1 in 44 American children on the autism spectrum, nearly 2.5 times increase in the prevalence of ASD since first reported in 2000. Studies also show that autism is over four times more common among boys than girls. An estimated 1 out of 27 boys and 1 in 116 girls are diagnosed with autism in the United States. ASD affects over 3 million people in the U.S. and tens of millions worldwide.

We don’t yet know all the reasons for the increase in prevalence.

What causes autism?

Not long ago, the answer to this question would have been, “We have no idea.” Research is now delivering the answers. First and foremost, we now know that there is no one cause of autism, just as there is no one type of autism. Over the last five years, scientists have identified more than 100 autism-risk genes. In about 15 to 30 percent of cases, a specific genetic cause of a person’s autism can now be identified. However, most cases involve a complex and variable combination of genetic risk and environmental factors that influence early brain development.

In other words, in the presence of a genetic predisposition to autism, non-genetic or environmental influences may further increase a child’s risk.

The clearest evidence of environmental risk factors involves events before and during birth. They include:

  • Advanced parental age at the time of conception (both mom and dad)
  • Maternal illness during pregnancy
  • Extreme prematurity
  • Very low birthweight and certain difficulties during birth, especially those involving lack of oxygen to the baby
  • Mother's exposure to high levels of pesticides and air pollution

These factors by themselves do not cause autism. Rather, in combination with genetic risk factors, they appear to modestly increase risk.

Increasingly, researchers are looking at the role of the immune system, metabolic factors, the microbiome (all the bacteria and other organisms that live on our skin and inside our digestive tract), and other biological processes. Autism Speaks is working to increase awareness and investigation of these and other issues, where further research has the potential to improve the lives of those on the autism spectrum and their families.

Language in the autism community

Children and adults with autism and their families all have very different experiences from one another. As a result of these unique experiences, there are different perspectives across the community on a variety of subjects, including language and terminology. Many people who meet the criteria for ASD have adopted the term “autistic” to describe their differences. Many self-described autistics prefer that their behavior not be depicted as pathological, but rather as a natural variation in human behavior. While we intentionally use medical language to describe ASD throughout this kit, we also recognize that for some, autism can be thought of simply as a difference in social behavior.

There are also conversations in the community about the preference of identity-first language (such as “autistic adult”) compared to person-first language (such as “adult with autism spectrum disorder”). Many advocates feel autism is a part of who they are as a person and not only a diagnosis. This highlights the need for sensitivity, understanding and acceptance of autistic people of all ages and their preferences for how they describe themselves.

Similarly, health care providers will use medical terminology when discussing your child’s diagnosis and treatment plans. Some of this language will be important when advocating for your child. You may choose to use different language when talking about autism outside of medical or other settings. Your family’s experience is unique and you can talk about autism however you’d like!