Autism affects children of all races and nationalities, but certain factors increase a child's risk. They include:
Boys are four to five times more likely to develop autism than girls are.
Families who have one child with autism have an increased risk of having another child with the disorder. It's also not uncommon for the parents or relatives of an autistic child to have minor problems with social or communication skills themselves or to engage in certain autistic behaviors.
Children with certain medical conditions have a higher than normal risk of having autism. These conditions include fragile X syndrome, an inherited disorder that causes intellectual problems; tuberous sclerosis, a condition in which benign tumors develop in the brain; the neurological disorder Tourette syndrome; and epilepsy, which causes seizures.
There may also be a connection between children born to older parents and autism, but more research is necessary to establish this link.