Autism Spectrum Disorder

Definition

Autism spectrum disorder (ASD) is a neurobiologic disorder with onset in early childhood. The key features are impairment in social communication and social interaction accompanied by restricted and repetitive behaviors. The presentation of ASD can vary significantly from one individual to another, as well as over the course of development for a particular child. There is currently no diagnostic biomarker for ASD. Accurate diagnosis therefore requires careful review of the history and direct observation of the child's behavior.

Diagnostic Criteria and Symptoms

The diagnostic criteria in the Diagnostic and Statistical Manual, Fifth Edition (DSM-5) focus on symptoms in two primary domains ( Table 54.1 ). To meet criteria for ASD, the symptoms need to have been present since the early developmental period, significantly impact functioning, and not be better explained by the diagnoses of intellectual disability (ID) or global developmental delay (GDD; Chapter 53 ). Table 54.2 provides associated features not included in DSM-5 criteria.

Table 54.1

DSM-5 Diagnostic Criteria for Autism Spectrum Disorder

A
Persistent deficits in social communication and social interaction across multiple contexts, as manifested by the following, currently or by history:
- 1
  Deficits in social-emotional reciprocity.
- 2
  Deficits in nonverbal communicative behaviors used for social interaction.
- 3
  Deficits in developing, maintaining, and understanding relationships.
B
Restricted, repetitive patterns of behavior, interests, or activities, as manifested by at least 2 of the following, currently or by history:
- 1
  Stereotyped or repetitive motor movements, use of objects, or speech.
- 2
  Insistence on sameness, inflexible adherence to routines, or ritualized patterns of verbal or nonverbal behavior.
- 3
  Highly restricted, fixated interests that are abnormal in intensity or focus.
- 4
  Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment.
C
Symptoms must be present in the early developmental period (may not become fully manifest until social demands exceed limited capacities, or may be masked by learned strategies in later life).
D
Symptoms cause clinically significant impairment in social, occupational, or other important areas of current functioning.
E
These disturbances are not better explained by intellectual disability (intellectual developmental disorder) or global developmental delay.

Table 54.2

For version with full references, see Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Washington DC, 2013, American Psychiatric Association. Adapted from Lai MC, Lombardo MV, Baron-Cohen S: Autism, Lancet 383:896–910, 2014.

Associated Features of Autism Not in DSM-5 Criteria

Atypical language development and abilities
- Age <6 yr: frequently disordered and delayed in comprehension; two-thirds have difficulty with expressive phonology and grammar
- Age ≥6 yr: disordered pragmatics, semantics, and morphology, with relatively intact articulation and syntax (i.e., early difficulties are resolved)
Motor abnormalities: motor delay; hypotonia; catatonia; deficits in coordination, movement preparation and planning, praxis, gait, and balance

Previously, ASD was grouped under the heading of pervasive developmental disorders (PDDs) and included a variety of subdiagnoses, including autistic disorder, PDD not otherwise specified (PDD-NOS), and Asperger disorder . Research did not support these as distinct conditions; in the current diagnostic framework, any individual previously diagnosed with 1 of these conditions should be diagnosed with ASD.

Symptoms can present early in infancy, with reduced response to name and unusual use of objects being strong predictors for risk of ASD. However, symptoms before age 12 mo are not as reliably predictive of later diagnosis. Individuals with milder severity may not present until preschool or school age, when the social demands for peer interaction and group participation are higher.

Social Communication and Social Interaction

Individuals with ASD have difficulty understanding and engaging in social relationships. The problems are pervasive and impact 3 major areas: reciprocal social interactions (social-emotional reciprocity), nonverbal communication, and understanding of social relationships. The presentation can vary with severity and developmental functioning. Diagnosis of ASD requires the presence of symptoms from all 3 categories ( Table 54.3 ).

Table 54.3

Adapted from Baird G, Douglas HR, Murphy MS: Recognizing and diagnosing autism in children and young people: summary of NICE guidance. BMJ 343:d6360, 2011, Box 1, p 901.

Signs and Symptoms of Possible Autism in Preschool Children (or Equivalent Mental Age)

Social Interaction and Reciprocal Communication Behaviors

Spoken Language

Language delay (in babbling or using words; e.g., using <10 words by age 2 yr).
Regression in, or loss of, use of speech.
Spoken language (if present) may include unusual features, such as vocalizations that are not speech-like; odd or flat intonation; frequent repetition of set words and phrases (echolalia); reference to self by name or “you” or “she” or “he” beyond age 3 yr.
Reduced and/or infrequent use of language for communication; e.g., use of single words, although able to speak in sentences.

Responding to Others

Absent or delayed response to name being called, despite normal hearing.
Reduced or absent responsive social smiling.
Reduced or absent responsiveness to other people's facial expressions or feelings.
Unusually negative response to the requests of others (“demand avoidance” behavior).
Rejection of cuddles initiated by parent or caregiver, although the child may initiate cuddles.

Interacting With Others

Reduced or absent awareness of personal space, or unusually intolerant of people entering their personal space.
Reduced or absent social interest in others, including children of own age—may reject others; if interested in others, child may approach others inappropriately, seeming to be aggressive or disruptive.
Reduced or absent imitation of others' actions.
Reduced or absent initiation of social play with others; plays alone.
Reduced or absent enjoyment of situations that most children like; e.g., birthday parties.
Reduced or absent sharing of enjoyment.

Eye Contact, Pointing, and Other Gestures

Reduced or absent use of gestures and facial expressions to communicate (although may place an adult's hand on objects).
Reduced and poorly integrated gestures, facial expressions, body orientation, eye contact (looking at people's eyes when speaking), and speech used in social communication.
Reduced or absent social use of eye contact (assuming adequate vision).
Reduced or absent “joint attention” (when 1 person alerts another to something by means of gazing, finger pointing, or other verbal or nonverbal indication for the purpose of sharing interest). This would be evident in the child from lack of:
- Gaze switching
- Following a point (looking where the other person points to—may look at hand)
- Using pointing at or showing objects to share interest

Ideas and Imagination

Reduced or absent imagination and variety of pretend play.

Unusual or Restricted Interests and/or Rigid and Repetitive Behaviors

Repetitive “stereotypic” movements such as hand flapping, body rocking while standing, spinning, and finger flicking.
Repetitive or stereotyped play; e.g., opening and closing doors.
Over focused or unusual interests.
Excessive insistence on following own agenda.
Extremes of emotional reactivity to change or new situations; insistence on things being “the same.”
Overreaction or underreaction to sensory stimuli, such as textures, sounds, or smells.
Excessive reaction to the taste, smell, texture, or appearance of food, or having extreme food fads.

Social-Emotional Reciprocity

Reduced social interactions in ASD may range from active avoidance or reduced social response to having an interest in, but lacking ability to initiate or sustain, an interaction with peers or adults. A young child with ASD may not respond when his name is called, may exhibit limited showing and sharing behaviors, and may prefer solitary play. In addition, the child may avoid attempts by others to play and may not participate in activities that require taking turns, such as peek-a-boo and ball play. An older child with ASD may have an interest in peers but may not know how to initiate or join in play. The child may have trouble with the rules of conversation and may either talk at length about an area of interest or abruptly exit the interaction. Younger children often have limited capacity for imaginative or pretend play skills. Older children may engage in play but lack flexibility and may be highly directive to peers. Some children with ASD interact well with adults but struggle to interact with same-age peers.

Nonverbal Communicative Behavior

Difficulties with nonverbal communication may manifest as reduced use of eye contact and gestures such as pointing. Children may also show reduced awareness or response to the eye gaze or pointing of others. They may use eye contact only when communicating a highly preferred request or may have difficulty coordinating the use of nonverbal with verbal communication. Children with ASD may have limited range of facial expression or expressed emotion.

Developing, Maintaining, and Understanding Relationships

Children with ASD have limited insight regarding social relationships. They have difficulty understanding the difference between a true friend and a casual acquaintance. They have trouble picking up on the nuances of social interactions and understanding social expectations for polite behavior. They may have reduced understanding of personal boundaries and may stand too close to others. In addition, they can have trouble understanding and inferring others' emotions and are less likely to share emotion or enjoyment with others. Adolescents and young adults have difficulty engaging in group interactions and navigating romantic relationships.

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