Autism spectrum disorder is a serious neurodevelopmental disorder that impairs a child's ability to communicate and interact with others. It also includes restricted repetitive behaviors, interests and activities. These issues cause significant impairment in social, occupational and other areas of functioning.

Autism spectrum disorder (ASD) is now defined by the American Psychiatric Association's Diagnosis and Statistical Manual of Mental Disorders (DSM-5) as a single disorder that includes disorders that were previously considered separate autism, Asperger's syndrome, childhood disintegrative disorder and pervasive developmental disorder not otherwise specified.

The term "spectrum" in autism spectrum disorder refers to the wide range of symptoms and severity. Although the term "Asperger's syndrome" is no longer in the DSM, some people still use the term, which is generally thought to be at the mild end of autism spectrum disorder.

The number of children diagnosed with autism spectrum disorder is rising. It's not clear whether this is due to better detection and reporting or a real increase in the number of cases, or both.

While there is no cure for autism spectrum disorder, intensive, early treatment can make a big difference in the lives of many children.

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Excerpt from:
Autism spectrum disorder - Mayo Clinic