You can draw a straight line from the initial descriptions of many conditions—claustrophobia, for example, or vertigo—to their diagnostic criteria. Not so with autism. Its history has taken a less direct path with several detours, according to Jeffrey Baker, professor of pediatrics and history at Duke University in Durham, North Carolina.

Autism was originally described as a form of childhood schizophrenia and the result of cold parenting, then as a set of related developmental disorders, and finally as a spectrum condition with wide-ranging degrees of impairment. Along with these shifting views, its diagnostic criteria have changed as well.

Here is how the Diagnostic and Statistical Manual of Mental Disorders (DSM), the diagnostic manual used in the United States, has reflected our evolving understanding of autism.

Why was autism initially considered a psychiatric condition?

When Leo Kanner, an Austrian-American psychiatrist and physician, first described autism in 1943, he wrote about children with “extreme autistic aloneness,” “delayed echolalia” and an “anxiously obsessive desire for the maintenance of sameness.” He also noted that the children were often intelligent and some had extraordinary memory.

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