Definition of Autism:

Autism is a developmental disorder that appears in the first 3 years of life, and affects the brain's normal development of social and communication skills.

Causes, incidence, and risk factors:

Autism is a physical condition linked to abnormal biology and chemistry in the brain. The exact causes of these abnormalities remain unknown, but this is a very active area of research. There are probably a combination of factors that lead to autism.

Genetic factors seem to be important. For example, identical twins are much more likely than fraternal twins or siblings to both have autism. Similarly, language abnormalities are more common in relatives of autistic children. Chromosomal abnormalities and other nervous system (neurological) problems are also more common in families with autism.

A number of other possible causes have been suspected, but not proven. They involve:

• Diet
• Digestive tract changes
• Mercury poisoning
• The body's inability to properly use vitamins and minerals
• Vaccine sensitivity

AUTISM AND VACCINES

Many parents are worried that some vaccines are not safe and may harm their baby or young child. They may ask their doctor or nurse to wait, or even refuse to have the vaccine. However, it is important to also think about the risks of not having the vaccination.

Some people believe that the small amount of mercury (called thimerosal) that is a common preservative in multidose vaccines causes autism or ADHD. However, studies have NOT shown this risk to be true.

The American Academy of Pediatrics, and The Institute of Medicine (IOM) agree that no vaccine or component of any vaccine is responsible for the number of children who are currently being diagnosed with autism. They conclude that the benefits of vaccines outweigh the risks.

All of the routine childhood vaccines are available in single-dose forms that do not contain added mercury.

The Centers for Disease Control and Prevention website provides further information.

HOW MANY CHILDREN HAVE AUTISM?

The exact number of children with autism is not known. A report released by the U.S. Centers for Disease Control and Prevention (CDC) suggests that autism and related disorders are more common than previously thought. It is unclear whether this is due to an increasing rate of the illness or an increased ability to diagnose the illness.

Autism affects boys 3 - 4 times more often than girls. Family income, education, and lifestyle do not seem to affect the risk of autism.

Some doctors believe the increased incidence in autism is due to newer definitions of autism. The term "autism" now includes a wider spectrum of children. For example, a child who is diagnosed with high-functioning autism today may have been thought to simply be odd or strange 30 years ago.

Other pervasive developmental disorders include:

• Asperger syndrome (like autism, but with normal language development)
• Rett syndrome (very different from autism, and only occurs in females)
• Childhood disintegrative disorder (rare condition where a child learns skills, then loses them by age 10)
• Pervasive developmental disorder - not otherwise specified (PDD-NOS), also called atypical autism