Autism Spectrum Disorders Health Center

Understanding Autism -- the Basics

What Is Autism?

Autism is a complex neurobehavioral disorder that includes impairments in social interaction and developmental language and communication skills and rigid, repetitive behaviors. The disorder covers a large spectrum of symptoms, skills, and levels of impairment. It ranges in severity from a handicap that limits an otherwise normal life to a devastating disability that may require institutional care.

Children with autism have trouble communicating. They have trouble understanding what other people think and feel. This makes it very hard for them to express themselves either with words or through gestures, facial expressions, and touch.

A child with autism who is very sensitive may be greatly troubled -- sometimes even pained -- by sounds, touches, smells, or sights that seem normal to others.

Children who are autistic may have repeated body movements such as rocking or hand flapping. They may have unusual responses to people, attachments to objects, resistance to change in their routines, or aggressive or self-injurious behavior. At times they may seem not to notice people, objects, or activities in their surroundings. Some children with autism may also develop seizures. And in some cases, those seizures may not occur until adolescence.

Many people with autism are cognitively impairted to some degree. In contrast to more typical cognitive impairment, which is characterized by relatively even skill development, people with autism show uneven skill development. They may have problems in certain areas, especially the ability to communicate and relate to others. But they may have unusually developed skills in other areas, such as drawing, creating music, solving math problems, or memorizing facts. For this reason, they may test higher -- perhaps even in the average or above-average range -- on nonverbal intelligence tests.

Autism typically appears during the first three years of life. Some children show signs from birth. Others seem to develop normally at first, only to slip suddenly into symptoms when they are 18 to 36 months old. Autism is four times more common in boys than in girls. It knows no racial, ethnic, or social boundaries. Family income, lifestyle, or educational levels do not affect a child's chance of being autistic. 

Autism is said to be increasing; however, it is not entirely clear whether the increase is related to changes in how it is diagnosed or is a true increase in the incidence of the disease.

Some of the different types of autism spectrum disorders include:

• Autistic disorder. This is what most people think of when they hear the word "autism." It refers to problems with social interactions, communication, and imaginative play in children younger than 3 years.
• Asperger's syndrome. These children don't have a problem with language -- in fact, they tend to score in the average or above-average range on intelligence tests. But they have the same social problems and limited scope of interests as children with autistic disorder.
• Pervasive developmental disorder or PDD -- also known as atypical autism. This is a kind of catch-all category for children who have some autistic behaviors but who don't fit into other categories.
• Rett syndrome. Known to occur mainly in girls, children with Rett syndrome start developing normally but begin to lose their communication and social skills. Beginning at the age of 1 to 4 years, repetitive hand movements replace purposeful use of the hands.
• Childhood disintegrative disorder. These children develop normally for at least two years and then lose some or most of their communication and social skills. This is an extremely rare disorder and its existence as a separate condition is a matter of debate among many mental health professionals.