Autism tends to run in families, suggesting a genetic link. Because people with autism can be vastly different, scientists suspect a number of genes are responsible. Ongoing research is targeted at pinpointing these genes. Some experts also believe that environmental factors may play a part in causing autism, although scientists have studied several factors, including vaccines, and have yet to identify such a cause.
Brain scans of people with autism have shown abnormalities in several areas of the brain, including those responsible for emotion and social relations. Other studies suggest that people with autism have high levels of the neurotransmitter serotonin, a chemical that sends messages in the brain. However, these findings are preliminary, and ongoing studies seek to explain the brain and autism.
