What are Autism Spectrum Disorders?

Autism spectrum disorders (ASD) represent a range of neurodevelopmental disorders including Autism, Asperger’s Syndrome, and Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS). Each of these disorders is characterized by three sets of behavioral features: 1) impairment in social interaction, 2) communication deficits (both verbal and nonverbal), and 3) restricted, repetitive behaviors including decreased imaginative play, stereotyped behaviors and inflexible adherence to routines. The degree to which these behaviors are manifested may vary between autism, Asperger’s Syndrome, and PDD-NOS, as well as between each affected individual.

Autism was first described by Leo Kanner in 1943. Kanner noted social isolation, impaired communication, and a strong need for sameness amongst 11 patients with whom he worked. He coined the term Early Infantile Autism to describe this pattern of behavior. Less than one year later, an Austrian pediatrician named Hans Asperger reported a lack of social understanding, one-sided conversations, and intense absorption in a special interest amongst 4 boys with whom he worked (though some argue that his work was based on hundreds of children he had followed up to the time of his writing). This pattern came to be referred to as Asperer’s Syndrome. Amazingly, despite the clear overlap in the behavioral features of their patients and the coincident timing of their respective reports, Kanner and Asperger did not know about each other’s work!

The core features of ASD have remained similar to Kanner’s and Asperger’s original descriptions. Much has been learned about ASD since these scientists’ writing as well. For example, we now know that ASD are neurodevelopmental disorders; that is, they are not caused by early parenting issues but rather reflect neurological differences. ASD disproportionately affect males at a rate of ~3-4:1. Approximately 40-75% of individuals with autism have significant cognitive impairment in the mentally retarded range (i.e., IQ < 70), and a subset of affected individuals do not develop any verbal language. ASD also may be associated with certain medical conditions, such as seizure disorder, fragile X syndrome, tuberous sclerosis, and other neurological and genetic disorders.

Despite an increased knowledge of ASD and major research advances in the past two decades, many questions remain unanswered. For example, while ASD once were believed to be rare (~4-5 per 10,000), studies performed over the past several years documented increased prevalence rates within both the US and other countries. Scientists are not sure why the prevalence of ASD has increased, though a broadening of the definition as well as professionals’ increased knowledge of how to identify ASD certainly have played a role. Many other ideas, such as exposure to mercury within immunizations, have been offered but lack any scientific support. Researchers around the world, including those at UIC, currently are investigating possible explanations.

The genetic and neurobiological mechanisms of ASD are the subjects of current research both at UIC and throughout the international scientific community. Autism is now recognized to have a significant genetic component. Family members of affected individuals face a much higher risk of developing autism (though the majority of siblings do not develop autism). Characteristics of autism, such as language processing deficits and difficulty in social interactions, have been found to more modest degrees in family members of individuals with autism. However, the mode of transmission and the genes involved are not yet known.

Specific abnormalities in brain development contributing to ASD are yet to be established. Without this knowledge, rational treatment and behavioral interventions are limited, as is our understanding of how ASD develop early in life. New and exciting tools, such as MRI, are now allowing researchers to investigate structural and functional brain patterns unique to ASD. These advances will continue to help develop and document the effectiveness of treatment programs for affected individuals. This is a promising time for those interested in understanding how best to help individuals diagnosed with ASD.