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Diagnosis, genetics, and prevalence

Diagnostic criteria

The diagnosis of autism has been defined in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (known as DSM-5). The DSM-5 is the 2013 update of the DSM-4. There were significant changes made to the diagnostic criteria and categories.

  • DSM-5 no longer includes the diagnoses of Autistic Disorder, Asperger syndrome, Pervasive Developmental Disorder Not Otherwise Specified (or PDD-NOS), and Childhood Disintegrative Disorder. The diagnosis for all is now Autism Spectrum Disorder (ASD) with no separate sub-diagnoses.
  • The three areas of symptoms from DSM-4 (social reciprocity, communicative intent, and restrictive and repetitive behaviors) were reduced to only two areas:
  • Social communication/interaction
  • Restrictive and repetitive behaviors

In the area of social communication/interaction, the challenges must be persistent and occur across contexts for a diagnosis of ASD. They must include all of the following symptoms:

  • Problems with establishing and/or maintaining back-and-forth conversations and interactions; inability to initiate interactions; problems sharing attention, emotions or interests with others.
  • Significant problems maintaining relationships; includes inability to engage in pretend play as a child, or age-appropriate social activities; problems adjusting to different social expectations.
  • Problems with nonverbal communications, such as eye contact, facial expressions, tone of voice and gestures

In the area of restricted and repetitive behavior, the diagnosis of Autism Spectrum Disorder (ASD) requires two of the following four symptoms:

  • Stereotyped or repetitive speech, motor movements or use of objects.
  • Excessive adherence to routines and resistance to change; ritualized patterns of behavior, either verbal or nonverbal
  • Abnormal intensity and focus on extremely restricted interests
  • Over or under reaction to sensory input; or, unusual interests in sensory inputs from the environment

Symptoms must be present in early childhood but may not become fully evident until social demands exceed the child’s capacities. Symptoms need to be functionally impairing and not better described by another DSM-5 diagnosis.

The new DSM-5 criteria also established a new symptom structure that recognizes differences in pattern of onset of symptoms as well as co-occurring symptoms such as Attention Deficit Hyperactivity Disorder (ADHD), anxiety, mood disorders; and co-occurring medical conditions such as seizure disorders, other general medical conditions such as diabetes or celiac disease. The severity of symptoms within each of the two areas of diagnostic criteria is also defined based on the level of support required for each symptom.

Finally, the DSM-5 criteria established a Social Communication Disorder for individuals with deficits in the social use of language, but do not have the restricted interests or repetitive behavior you see in autism spectrum disorders.

Genetics of Autism Spectrum Disorder

ASD can be diagnosed as part of other genetic syndromes, including Fragile X syndrome, Rett syndrome, tuberous sclerosis, neurofibromatosis, 22q deletion, and PTEN hamartoma tumor syndrome syndrome.  Individuals with these conditions usually present with other symptoms and the diagnosis can be confirmed by testing one gene. Individuals who have ASD without other symptoms are referred to as having isolated ASD.  Studies have shown that the genes identified as being highly associated with isolated ASD fall into two main functional categories:

  • One category includes the genes related to the development and regulation or function of synapses (the connections between nerves).
  • The other category includes genes related to chromatin (a DNA-protein complex) that is involved in the regulation of gene expression. 

In addition to the specific genes that are being identified, advances in genetic testing have identified very tiny deletions and duplications in genes as being associated with autism. These deletions and duplications involve multiple genes and often occur in the child alone and are not carried by either parent (de novo or “new” mutation). 

  • The more common de novo deletion/duplications include: 2q37, 7q11, 15q11-13, 16p11, 22q11.2 and 22q13.3.
  • The most common recurring changes are deletions and duplications of 7q11, 15q11.2-13.3 and 16p11.2.

These genetic differences may occur in family members without ASD, and are thought to cause an increased chance of ASD. See Genetics Home Reference for more information.

Prevalence

Autism and Developmental Disabilities Monitoring (ADDM) Network

The ADDM Network is a group of programs funded by the Centers for Disease Control & Prevention (CDC) to estimate the number of children with ASD and other developmental disabilities living in different areas of the United States. The ADDM Network sites all collect data using the same methods.

CDC estimates that 1 in 68 children were identified with an ASD in 2010; check their website for updated numbers. This data comes from the ADDM Network, which estimated the number of 8-year-old children with ASD living in 11 communities throughout the United States in 2010.

Common questions related to diagnosis of Autism  Spectrum Disorder using DSM-5 criteria

What does Functional Impairment mean?

This means that the child has difficulty in an area of development that impacts his ability to function easily with his peers. Symptoms may be present in early childhood, but may not become evident until social demands on the child exceed his or her capacities. For example, the child can function socially in a preschool setting (where demands may be lower), but is then unable to cope with the social demands of a kindergarten classroom. Symptoms must impair how the child functions in the world and not be better described by another DSM-5 diagnosis. 

Is Rett syndrome still considered part of ASD?

No, Rett syndrome is a neurologic disorder that is no longer a sub-diagnosis under ASD, although patients with Rett syndrome may have ASD.

Is there a need for re-diagnosis?

Because almost all children with DSM-4 confirmed autistic disorder or Asperger syndrome also meet diagnostic criteria under DSM-5, re-diagnosis is not necessary. Referral for reassessment should be based on clinical concern. Children given a PDD-NOS diagnosis who had few DSM-IV symptoms of autism or who were given the diagnosis as a “placeholder” might be considered for more specific diagnostic evaluation.

Will some already diagnosed with Asperger syndrome keep the label of Asperger syndrome?

Peoples may wish to continue to self-identify as having Asperger syndrome, although the DSM-5 diagnostic category will be ASD.

Should Speech and Language still be evaluated?

Yes, clinicians should note that children with ASD also should be evaluated for a speech and language diagnosis in addition to the ASD to inform appropriate therapy.

What is a Social Communication Disorder?

The DSM-5 includes a new diagnostic category called Social Communication Disorder. Children with social communication disorder may have social difficulty with understanding, producing and being aware of conversational norms. This difference is not caused by delayed cognition or other language delays. It may be a distinct diagnosis or may occur in addition to other conditions, such as autism spectrum disorder (see American Society of Human Genetics for more detail).