What Is Autism and Autism Spectrum Disorder?

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Unlike many health conditions, autism, a disorder that involves abnormal development and function of the brain, is unique in that it is considered a spectrum disorder. Autism spectrum disorder (ASD) results in difficulties in social interaction and in verbal and nonverbal communication. ASD is also characterized by the presence of repetitive movements, such as hand flapping or body rocking, an insistence on sameness, and a resistance to change. In some cases, people with ASD show behaviors of aggression or self-injury.

Brief History

Prior to 2013, autism disorders were recognized as distinct subtypes, such as autistic disorder, childhood disintegrative disorder, and Asperger syndrome. However, in 2013, the DSM-5 diagnostic manual merged all of these disorders under the umbrella diagnosis of ASD.

Major Brain Structure Implicated in Autism
Major Brain Structure in Autism

ASD is associated with intellectual disability, difficulties in motor coordination, and attention and physical health issues. However, some people with ASD do excel in specific areas, such as music, math or art. Not all individuals with autism have cognitive impairments and some have typical or even above average IQs.

While signs of ASD don’t emerge until between ages 2 and 3, the roots of ASD appear to be in early brain development. The Centers for Disease Control and Prevention have reported that around 1 in 68 children in the United States are identified as being on the autism spectrum. Autism was first characterized in 1943 by Leo Kanner. At the time, the prevalence of autism was thought to be 1 out of every 2,000 children.

Source of Autism

While the prevalence of autism has increased in the US, there is no established explanation for the rise in ASD, but improved diagnosis and awareness may be one explanation, according to Autism Speaks. The popular theory that vaccines cause autism has been disproven by numerous studies conducted worldwide, confirmed the Autism Science Foundation.

While the cause of autism is unknown, researchers have determined that autism is a strongly inherited disorder. For example, scientists have found that if one identical twin has autism then there is an 80% to 90% chance that the other twin will be diagnosed with ASD. Among non-identical twins, the chance drops drastically to just 3% to 10% that both twins will develop ASD. The chance that siblings will both be effects is also around 3% to 10%.