What causes autism spectrum disorder (ASD)?

What causes autism spectrum disorder (ASD)?

There is no clear-cut cause of ASD. Some causes that are supported by research include genetic and some environmental factors. Specific genetic causes can only be identified in 10% to 20% of cases. These cases include specific genetic syndromes associated with ASD and rare changes in the genetic code.

Risk factors include older parental age, low birth weight, prematurity and maternal use of valproic acid or thalidomide during pregnancy, among others. This field of study is an active one for research.