Autism is a brain disorder that is associated with a range of developmental problems, mainly in communication and social interaction. The first signs of this disorder typically appear before age 3. Although treatment has improved greatly in the past few decades, autism cannot be cured. It persists throughout life.

It's estimated that three to six of every 1,000 children have autism. A recent increase in the number of autism cases in the United States may be the result of improved diagnosis and changes in diagnostic criteria.

The disorder occurs three to four times more often in boys than in girls. The severity of symptoms is variable. Some children with autism will grow up able to live independently, while others may always need supportive living and working environments.

The cause of autism isn't clear, and there's no cure. But intensive, early treatment can make a difference.

Autism has no single, identifiable cause. The disorder seems to be related to abnormalities in several regions of the brain. Researchers have identified a number of gene defects associated with autism.

Families with one autistic child have a one in 20 chance of having a second child with the disorder. In some cases, relatives of autistic children show mild impairments in social and communication skills or engage in repetitive behaviors.

Children with symptoms of autism have a higher than normal risk of also having:

Note: Some people believe autism is caused by vaccines - particularly the Measles-Mumps-Rubella vaccine (MMR), as well as vaccines containing Thimerosal (a preservative that contains a very small amount of mercury). But extensive studies have shown no link between vaccines and autism.

Babies develop at their own pace, and many don't follow exact timelines found in some parenting books. But children with autism usually show some signs of delayed development by 18 months. If you suspect that your child may have autism, discuss your concerns with your doctor. The earlier treatment begins, the more effective it will be.

Your doctor may recommend further evaluation if your child:

In general, children with autism have problems in three crucial areas of development — social skills, language and behavior. The most severe autism is marked by a complete inability to communicate or interact with other people.

Because the symptoms of autism vary widely, two children with the same diagnosis may act quite differently and have strikingly different skills.

If your child has autism, he or she may develop normally for the first few months — or years — of life and then later become less responsive to other people, including you. You may recognize the following signs in the areas of social skills, language and behavior:

Young children with autism also have a hard time sharing experiences with others. When someone reads to them, for example, they're unlikely to point at pictures in the book. This early-developing social skill is crucial to later language and social development.

As they mature, some children with autism become more engaged with others and show less marked disturbances in behavior. Some, usually those with the least severe impairments, eventually may lead normal or near-normal lives. Others, however, continue to have severe impairments in language or social skills, and the adolescent years can mean a worsening of behavior problems.

The majority of children with autism are slow to acquire new knowledge or skills. However, some children with autism have normal to high intelligence. These children learn quickly yet have trouble communicating, applying what they know in everyday life and adjusting in social situations. An extremely small number of children with autism are "autistic savants" and have exceptional skills in a specific area, such as art or math.

Your child's doctor will look for signs of developmental delays at regular checkups. If your child shows some signs of autism, you may be referred to a specialist in treating children with autism. This specialist, working with a team of professionals, can perform a formal evaluation for the disorder.

Because autism varies widely in severity and manifestations, making a diagnosis may be difficult. There isn't a medical test to pinpoint the disorder. Instead, a formal evaluation consists of observing your child and talking to you about how your child's social skills, language skills and behavior have developed and changed over time. To help reach a diagnosis, your child may undergo a number of developmental tests covering speech, language and psychological issues.

Although the signs of autism often appear by 18 months, the diagnosis sometimes isn't made until age 2 or 3, when there may be more obvious delays in language development. Early diagnosis is important because early intervention — preferably before age 3 — seems to be associated with the best chance for significant improvement.

There's no cure for autism, and there's no "one-size-fits-all" treatment. In fact, the range of home-based and school-based treatments and interventions for autism can be overwhelming. Your doctor can help identify resources in your area that may work for your child. Treatment options may include: