Cause and Risk Factors for Autism
The cause of autism is unknown. The disorder results from abnormalities in brain structure or function and the underlying cause usually cannot be identified. Patients with autism often have abnormalities in several areas of the brain. This may indicate that a disruption in fetal brain development contributes to the disorder.
Brain abnormalities may result from genetic (hereditary) or environmental (e.g., exposure to toxins) factors, metabolic disorders (e.g., serotonin deficiency), viral infections (e.g., German measles), or complications during pregnancy and delivery.
A single gene for autism has not been identified, but a group of unstable genes may trigger the disorder in some patients. According to a recent study, approximately 11% of autism cases may have a genetic component.
The measles-mumps-rubella vaccine (MMR) may contribute to autism in some cases; however, this potential link is controversial. More research is necessary to evaluate this possible link.
Medical conditions associated with an increased risk for autism include the following:
- Fragile X syndrome (more common in males; may cause mental retardation)
- Tuberous sclerosis (syndrome that causes seizures, mental disorders, and tumors)
- Congenital rubella syndrome (results from transmission of the rubella virus [causes German measles] in utero)
- Untreated phenylketonuria (PKU; hereditary disease caused by a defective enzyme)
