Autism Spectrum Disorders

There is considerable overlap among the different forms of autism. The wide variation in symptoms among children with autism, however, has led to the concept of autism spectrum disorder, or ASD.

ASDs affect one out of every 68 children in the U.S. They occur more often among boys than girls. While autism appears to be on the rise, it's unclear whether the growing number of diagnoses shows a real increase or comes from improved detection.

Early diagnosis is important. That's because early treatment can help a child with autism make significant gains in language and social skills.

 

Signs of Autism Spectrum Disorder

Autism spectrum disorders affect three different areas of a child's life:

  • Social interaction
  • Communication -- both verbal and nonverbal
  • Behaviors and interests

Each child with an ASD will have his or her own pattern of autism.

Sometimes, a child's development is delayed from birth. Some children seem to develop normally before they suddenly lose social or language skills. Others show normal development until they have enough language to demonstrate unusual thoughts and preoccupations.

In some children, a loss of language is the major impairment. In others, unusual behaviors (like spending hours lining up toys) seem to be the dominant factors.

Parents are usually the first to notice something is wrong. But a diagnosis of autism is often delayed. Parents or a physician may downplay early signs of autism, suggesting the symptoms are "just a phase" or a sign of a minor delay in development. Children with a possible autism spectrum disorder, though, should be evaluated by a professional team with experience in diagnosing autism.

Until recently, the types of ASD have been determined by guidelines in the diagnostic manual (DSM - IV) of the American Psychiatric Association. According to the CDC, the three main types of ASD are:

The DSM -IV also included two rare but severe autistic-like conditions -- Rett syndrome and childhood disintegrative disorder.

The new diagnostic manual has made some major changes in this list of disorders. It's unclear, though, how these changes will affect the way health professionals define exactly what is an autistic spectrum disorder.

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Asperger's Syndrome

The mildest form of autism, Asperger's syndrome (AS), affects boys three times more often than girls. Children with AS become obsessively interested in a single object or topic. They often learn all about their preferred subject and discuss it nonstop. Their social skills, however, are markedly impaired, and they are often awkward and uncoordinated.

Asperger's syndrome is mild compared to other ASDs. Also, children with AS frequently have normal to above average intelligence. As a result, some doctors call it "high-functioning autism." As children with AS enter adulthood, though, they are at high risk for anxiety and depression.

Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS)

This mouthful of a diagnosis applies to most children with autistic spectrum disorder. Children whose autism is more severe than Asperger's syndrome, but not as severe as autistic disorder, are diagnosed with PDD-NOS.

Autism symptoms in kids with PDD-NOS vary widely, making it hard to generalize. Overall, compared to children with other autistic spectrum disorders, children with PDD-NOS have:

  • Impaired social interaction (like all children with autistic spectrum disorder)
  • Better language skills than kids with autistic disorder but not as good as those with Asperger's syndrome
  • Fewer repetitive behaviors than children with Asperger's syndrome or autistic disorder
  • A later age of onset

No two children with PDD-NOS are exactly alike in their symptoms. In fact, there are no agreed-upon criteria for diagnosing PDD-NOS. In effect, if a child seems autistic to professional evaluators but doesn't meet all the criteria for autistic disorder, he or she has PDD-NOS.

Autistic Disorder

Children who meet more rigid criteria for a diagnosis of autism have autistic disorder. They have more severe impairments involving social and language functioning, as well as repetitive behaviors. Often, they also have mental retardation and seizures.

 

Rett Syndrome

Children with Rett syndrome often exhibit autistic-like behaviors. While Rett syndrome was originally believed to fall under the autism umbrella, it is now known that the disorder is caused by a genetic mutation and unrelated to ASD. If someone with Rett syndrome displays autism symptoms, then they also have ASD

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The Rett sydrome mutation usually occurs randomly, rather than being inherited. Treatment focuses on physical therapy and speech therapy to improve function.

Almost exclusively affecting girls, Rett syndrome is rare. About one in 10,000 to 15,000 girls develop this severe form of autism. Between 6 and 18 months of age, the child stops responding socially, wrings her hands habitually, and loses language skills. Coordination problems appear and can become severe. Head growth slows down significantly and by the age of two is far below normal.

Childhood Disintegrative Disorder

The most severe autistic spectrum disorder, childhood disintegrative disorder (CDD), is also the least common.

After a period of normal development, usually between ages 2 and 4, a child with CDD rapidly loses multiple areas of function. Social and language skills are lost, as well as intellectual abilities. Often, the child develops a seizure disorder. Children with childhood disintegrative disorder are severely impaired and don't recover their lost function.

Fewer than two children per 100,000 with an autistic spectrum disorder meet criteria for childhood disintegrative disorder. Boys are affected by CDD more often than girls.

WebMD Medical Reference Reviewed by Smitha Bhandari, MD on May 30, 2016

Sources

SOURCES:

National Institute of Mental Health: "Autism Spectrum Disorders."

National Institute of Neurological Disorders and Stroke: "Asperger Syndrome Fact Sheet."

Walker D. Journal of the American Academy of Child & Adolescent Psychiatry, 2004.

Willemsen-Swinkels S. Psychiatric Clinics of North America, 2002.

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