Autism Spectrum Disorders

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Autism Spectrum Disorders

• Chapter 20
• Susan Faja and Geraldine Dawson

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HISTORICAL CONTEXT

• Leo Kanner (1943)
• First characterized autism as a variety of
  behaviors including lack of social reciprocity
  and emotional awareness, delays in communication,
  atypical use of language, and repetitive
  interests and behaviors.
• Hans Asperger (1943)
• Described a high-functioning form of autism that
  characterized children as little professors
  with intense interests and the ability to provide
  lengthy descriptions of their interests.

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TERMINOLOGICAL AND CONCEPTUAL ISSUES

• Autism spectrum disorders include autistic
  disorder, Aspergers disorder, and pervasive
  developmental disorder not otherwise specified
  (PDD-NOS)
• DSM-IV diagnostic criteria include four types of
  impairments in each of three domains
• Social interaction, communication, and repetitive
  or restricted behaviors or interests.
• These symptoms typically appear before age 3.

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TERMINOLOGICAL AND CONCEPTUAL ISSUES

• Comorbidities
• Most commonly, ASD is accompanied by
  developmental delay or intellectual disability
  however, a significant portion of individuals
  with ASD has average to above average
  intelligence.
• Medical comorbidities, include sleep disorders,
  gastrointestinal disorders, psychiatric
  conditions, and seizures.
• Socioeconomic Considerations
• Affects individuals regardless of socioeconomic
  level (Fombonne, 1999, 2003).
• Parental education level, continues to be related
  to age of diagnosis (Fountain, King, Bearman,
  2011).
• Diagnosis is also delayed for children in the
  Medicaid system (Mandell et al., 2010).

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PREVALENCE

• ASD affects approximately 1 in 110 children in
  the United States (ADDM, 2009)
• Annual societal cost of more than 35 billion per
  year and approximately 3.2 million per
  individual (Ganz, 2007)
• Affects males more commonly than females, with a
  ratio of 4.5 to 1, and prevalence for boys is 1
  in 70 (ADDM, 2009)
• Affected females are more likely than males to
  have comorbid intellectual disability in the
  severe range (IQ lt 35)

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ETIOLOGICAL FORMULATIONS

Experience-based risk processes in autism
Risk processes
Outcome
Vulnerabilities
Altered neural circuitry Altered patterns of
interaction between child and environment

• Susceptibility genes
• Environmental risk factors

Full autism syndrome Broader autism phenotype
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GENETICS AND HERITABILITY

• Strong evidence for genetic influences in autism,
  yet the role of susceptibility genes is complex.
• Multiple genes interact to increase
  susceptibility to ASD by influencing gene
  expression or encoding functional changes in
  proteins that are part of complex regulatory
  networks.
• The expression and effects of many genes are
  influenced by environmental factors, offering
  hope that early intervention can alter genetic
  expression, brain development, and behavioral
  outcomes.

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ENVIRONMENTAL RISK FACTORS

• Advanced parental age, low birth weight, prenatal
  exposure to pollution and pesticides, maternal
  infection, and use of certain medications (e.g.,
  SSRIs) during pregnancy.
• Measles-mumps-rubella (MMR) vaccination
• Epidemiological studies have failed to confirm an
  association between the MMR vaccine and autism.
• Thimerosal, a preservative containing ethyl
  mercury that was added to many vaccines, has also
  been examined and no evidence of increased risk
  has been found (Parker, Schwartz, Todd,
  Pickering, 2004).

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DEVELOPMENTAL PROGRESSION

• Behavioral Symptoms Apparent in Infancy
• 6 and 12 eye contact declines
• 8 to 10 months infants are less likely to respond
  to their name
• 6-12 months directed vocalizations (e.g.,
  babbling or crying while looking at a person)
  decreased and spent longer fixating on a single
  object and had less active spontaneous visual
  exploration
• 12 months there is reduced orienting when called
  by name, less time spent looking at faces, and
  decreased social interest
• 12 to 24 months stereotyped movements and
  repetitive behaviors also emerge.

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DEVELOPMENTAL PROGRESSION

• Toddler-Preschool Period
• Cognitive, language, and behavioral difficulties
• Five key domains of social behavior are affected
• Social orienting
• Joint attention
• Attention to emotional cues
• Motor imitation
• Face processing

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ABNORMAL NEURAL DEVELOPMENT IN AUTISM

• Structural brain imaging in young children with
  autism
• 2- to 4-year-olds with ASD have larger total
  cerebral volumes.
• Neuroimaging of structural and functional
  connectivity in children with autism
• Differences in white matter (i.e., myelinated
  axons) abnormal minicolumn width and cell
  numbers, particularly in regions involved in
  higher-order behaviors, have led to understanding
  the neurobiology of autism as a disorder of
  connectivity (Minshew Williams, 2007).
• Electrophysiology in young children with autism
• Impairments in brain response in children with
  ASD by 6 months for processing eye gaze, and by
  age 3 for neural differentiation between the face
  of each childs mother and a stranger and slower
  processing of emotional content conveyed by
  faces.

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PROTECTIVE FACTORS

• Early comprehensive interventions
• Initiated during the preschool period and
  sustained for 2 to 4 years
• A significant impact on outcome in a large subset
  of children with autism, including significant
  gains in IQ, language, and educational placements
  (Rogers Vismara, 2008).
• Parent-delivered, targeted interventions
• More targeted approach
• Provides training in specific domains for the
  caregivers of children with ASD
• Interventions for older individuals with ASD
• Used with school-age children
• Group format
• Social skills interventions

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SYNTHESIS AND FUTURE DIRECTIONS

• Research focused on identifying autism
  susceptibility indices, early identification, and
  early intervention offer real hope for the
  future.
• As early identification and intervention become
  increasingly effective, the new challenge will be
  translating these scientific findings into social
  policy.