What Are the Causes of Autism?

Autism spectrum disorder (ASD) can look different in different people. It’s a developmental disability that affects the way people communicate, behave, or interact with others.

Experts don’t fully understand all of the causes of autism spectrum disorder. It seems to be genetic, but things such as parental age and prescription medications taken during pregnancy may be involved.

For instance:

• A person is more likely to be on the spectrum if a brother, sister, or parent is. But it doesn’t always run in families.
• About 10% of kids with ASD have a form of genetic disorder such as Down syndrome and fragile X syndrome.
• A large Danish study found a link between ASD and the advanced parental age of either parent.
• Women prescribed opioids just before pregnancy are likelier to have a child with ASD.

Some children who are on the spectrum start showing signs as young as a few months old. Others seem to have normal development for the first few months or years of their lives and then they start showing symptoms.

But up to half of parents of children with ASD noticed issues by the time their child reached 12 months, and between 80% and 90% noticed problems by 2 years. Children with ASD will have symptoms throughout their lives, but it’s possible for them to get better as they get older.

The autism spectrum is very wide. Some people might have very noticeable issues, others might not. The common thread is differences in social skills, communication, and behavior compared with people who aren’t on the spectrum.