Autism was first officially identified as a distinct medical condition in 1943 by Austrian-American psychiatrist Leo Kanner. In his landmark paper, Kanner described 11 children with unique behavioral traits including social withdrawal, delayed speech, and a strong desire for sameness in their environment. He called it "early infantile autism" and distinguished it from schizophrenia, which had previously included such symptoms under broader psychiatric diagnoses. Before Kanner's description, the term "autism" was used by Swiss psychiatrist Eugen Bleuler in 1911, but only to describe a symptom of schizophrenia, not as a separate condition. Additional important milestones include:
- In 1944, Hans Asperger described a related, milder form of autism (later called Asperger syndrome).
- Autism was officially categorized as a distinct condition in the Diagnostic and Statistical Manual of Mental Disorders (DSM) starting with DSM-III in 1980.
- The concept of autism as a spectrum disorder was further developed in subsequent DSM editions, notably DSM-IV in 1994 and DSM-5 in 2013.