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 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).

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 processesOutcome 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) 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).

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.

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

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 child’s mother and a stranger and slower processing of emotional content conveyed by faces.

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

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.