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Autism Fact Sheet (page 2)

— National Institute of Neurological Disorders and Stroke
Updated on Jul 26, 2007

How is autism diagnosed?

Autism varies widely in its severity and symptoms and may go unrecognized, especially in mildly affected children or when it is masked by more debilitating handicaps.  Doctors rely on a core group of behaviors to alert them to the possibility of a diagnosis of autism.  These behaviors are:    

  • impaired ability to make friends with peers
  • impaired ability to initiate or sustain a conversation with others
  • absence or impairment of imaginative and social play
  • stereotyped, repetitive, or unusual use of language
  • restricted patterns of interest that are abnormal in intensity or focus
  • preoccupation with certain objects or subjects
  • inflexible adherence to specific routines or rituals

Doctors will often use a questionnaire or other screening instrument to gather information about a child’s development and behavior.  Some screening instruments rely solely on parent observations; others rely on a combination of parent and doctor observations.  If screening instruments indicate the possibility of autism, doctors will ask for a more comprehensive evaluation.

Autism is a complex disorder.  A comprehensive evaluation requires a multidisciplinary team including a psychologist, neurologist, psychiatrist, speech therapist, and other professionals who diagnose children with ASDs.  The team members will conduct a thorough neurological assessment and in-depth cognitive and language testing.  Because hearing problems can cause behaviors that could be mistaken for autism, children with delayed speech development should also have their hearing tested. After a thorough evaluation, the team usually meets with parents to explain the results of the evaluation and present the diagnosis. 

Children with some symptoms of autism, but not enough to be diagnosed with classical autism, are often diagnosed with PDD-NOS.  Children with autistic behaviors but well-developed language skills are often diagnosed with Asperger syndrome.  Children who develop normally and then suddenly deteriorate between the ages of 3 to 10 years and show marked autistic behaviors may be diagnosed with childhood disintegrative disorder.  Girls with autistic symptoms may be suffering from Rett syndrome, a sex-linked genetic disorder characterized by social withdrawal, regressed language skills, and hand wringing. 

What causes autism?

Scientists aren’t certain what causes autism, but it’s likely that both genetics and environment play a role.     Researchers have identified a number of genes associated with the disorder.  Studies of people with autism have found irregularities in several regions of the brain.  Other studies suggest that people with autism have abnormal levels of serotonin or other neurotransmitters in the brain.  These abnormalities suggest that autism could result from the disruption of normal brain development early in fetal development caused by defects in genes that control brain growth and that regulate how neurons communicate with each other.  While these findings are intriguing, they are preliminary and require further study.  The theory that parental practices are responsible for autism has now been disproved. 

What role does inheritance play?

Recent studies strongly suggest that some people have a genetic predisposition to autism.  In families with one autistic child, the risk of having a second child with the disorder is approximately 5 percent, or one in 20.  This is greater than the risk for the general population.   Researchers are looking for clues about which genes contribute to this increased susceptibility.  In some cases, parents and other relatives of an autistic child show mild impairments in social and communicative skills or engage in repetitive behaviors.   Evidence also suggests that some emotional disorders, such as manic depression, occur more frequently than average in the families of people with autism. 

Do symptoms of autism change over time?

For many children, autism symptoms improve with treatment and with age.  Some children with autism grow up to lead normal or near-normal lives.  Children whose language skills regress early in life, usually before the age of 3, appear to be at risk of developing epilepsy or seizure-like brain activity.  During adolescence, some children with autism may become depressed or experience behavioral problems.  Parents of these children should be ready to adjust treatment for their child as needed.  

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