They can also be worse in some people than in others. Some of the more common signs are listed in the box to the right. Doctors aren't sure what causes autism. Certain medical problems or something in your child's surroundings may also play a role. In many cases, the cause of a child's autism is never known.
Boys are more likely than girls to have autism.
As doctors continue to study autism, they may learn more about what causes it. Vaccines are an important part of your child's health. If you have any concerns about the safety of vaccines, talk to your doctor. There is no lab test that can detect autism. Autism is often diagnosed when a baby or toddler doesn't behave as expected for his or her age.