Clinical characteristics of autism spectrum disorder

The following clinical characteristics are consistent with the DSM-5 diagnostic criteria for autism spectrum disorder (ASD):

  • impaired social communication and interaction across multiple contexts (eg deficits in social-emotional reciprocity, non-verbal communicative behaviours for social communication, developing, maintaining and understanding relationships)
  • restricted, repetitive patterns of behaviour, interests or activities (eg stereotyped or repetitive motor movements, use of objects or speech; insistence on sameness; highly restricted, fixated interests that are abnormal in intensity or focus; hypo- or hyper-reactivity to sensory stimuli).

Diagnostic criteria require that these characteristics must have been present since the early developmental period and must cause clinically significant impairment in social, occupational or other important areas of current functioning.

For a list of behavioural manifestations or ‘red flags’ that may indicate autism spectrum disorder, see ‘Red flags’ for autism spectrum disorder in children and adults.
Figure 1. ‘Red flags’ for autism spectrum disorder in children and adults.

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Girls are often more able to ‘camouflage’ behaviours and to copy social skills from peers, and may be more dreamy, distractible and creative compared with boys with autism spectrum disorder. The interests of girls with autism spectrum disorder can be similar to their peers but more intense; they may be more interested in animals and nature.

The severity of autism spectrum disorder can vary; DSM-5 has defined 3 levels, ranging from Level 1 (requiring support) to Level 3 (requiring very substantial support) across each of the diagnostic domains. When supports are not in place, a person with Level 1 severity autism spectrum disorder will have noticeable impairments, while a person with Level 3 severity autism spectrum disorder will have severe deficits and little or no intelligible speech. DSM-5 provides guidance on these distinctions.

Autism spectrum disorder may be accompanied by:

  • intellectual impairment
  • language impairment
  • clinical features of a known medical or genetic condition, or environmental cause (eg fetal alcohol exposure)
  • another neurodevelopmental, psychiatric or behavioural disorder
  • catatonia.

For more advice on co-occurring health conditions that are commonly associated with autism spectrum disorder, see Common health problems.