While the exact cause of autism is not known as of 2015, studies suggest that environmental factors, genetic predisposition, poor immune system performance, and abnormal brain growth and structures may cause autism, according to WebMD. Autism may also be caused by certain infections or problems at birth.
Research suggests that some people may be susceptible to autism because of genes passed down from their parents, notes WebMD. Some people with autism have abnormalities in certain regions of the brain, which suggests that autism may be caused by problems with neurological development while the baby is still unborn.
While it is generally not considered valid, one hypothesis is that the immune system may produce antibodies that cause autism in children, states WebMD. Another theory is that children with autism may experience rapid brain growth at a younger age than most children but have slower brain development later in life. Children with autism may also have larger brains at a younger age than other children.
Scientific research does not suggest that vaccinations cause autism, notes WebMD. Although some parents of children with autism have suggested that the measles, mumps, rubella vaccine may cause autism, scientific research does not indicate that this is true. It is believed that autism that occurs after an MMR vaccination is a coincidence, as the vaccine is typically administered with 12 to 15 months of the child being born.