Autism Spectrum Disorders

Chapter 20

Susan Faja and Geraldine Dawson

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.

TERMINOLOGICAL AND CONCEPTUAL ISSUES

Autism spectrum disorders include autistic disorder, Asperger’s 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.

TERMINOLOGICAL AND CONCEPTUAL ISSUES

ComorbiditiesMost 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).

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 < 35)

ETIOLOGICAL FORMULATIONS

Full autism syndrome

Broader autism phenotype

Altered neural circuitry Altered patterns of interaction between child and environment

Vulnerabilities Risk processes Outcome

Susceptibility genes

•Environmental risk factors

Experience-based risk processes in autism

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.

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) vaccinationEpidemiological 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).

DEVELOPMENTAL PROGRESSION

Behavioral Symptoms Apparent in Infancy6 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.

DEVELOPMENTAL PROGRESSION

Toddler-Preschool PeriodCognitive, language, and behavioral difficultiesFive key domains of social behavior are affected:

• Social orienting• Joint attention• Attention to emotional cues• Motor imitation• Face processing

ABNORMAL NEURAL DEVELOPMENT IN AUTISM

Structural brain imaging in young children with autism2- to 4-year-olds with ASD have larger total cerebral volumes.

Neuroimaging of structural and functional connectivity in children with autismDifferences 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 autismImpairments 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 child’s mother and a stranger and slower processing of emotional content conveyed by faces.

PROTECTIVE FACTORS

Early comprehensive interventionsInitiated 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 interventionsMore targeted approach Provides training in specific domains for the caregivers of children with

ASD

Interventions for older individuals with ASDUsed with school-age childrenGroup formatSocial skills interventions

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.