What Causes It?

Autism has more than one cause. Because autism runs in families, most researchers think that certain combinations of genes may predispose a person to autism. It's currently thought that there may be several different causes of autism. This suggests that there may be several different subtypes of autism.

When a pregnant woman is exposed to certain drugs or chemicals during pregnancy, her child is more likely to be autistic. These risk factors include the use of alcohol and the use of antiseizure drugs during pregnancy. In some cases, autism has been linked to untreated phenylketonuria (called PKU, an inborn metabolic disorder caused by the absence of an enzyme), rubella (German measles) and celiac disease (an inability to tolerate gluten in grains).

Exactly why autism happens isn't clear. Research suggests that it may arise from physical problems in parts of the brain that interpret sensory input and process language. Imbalances in brain chemicals also appear to play a role.

Researchers have no evidence that a child's psychological environment—such as how caregivers treat the child—causes autism.

Reviewed by Steven Spark, MD, on June 1, 2005