The first person formally diagnosed with autism was Donald Gray Triplett, an American man born on September 8, 1933, in Forest, Mississippi. His diagnosis was made by child psychiatrist Leo Kanner and published in 1943 in Kanner’s landmark paper “Autistic Disturbances of Affective Contact,” where Triplett was anonymized as “Case 1, Donald T.”

Quick Scoop

  • Who was the first person diagnosed with autism?
    Donald Gray Triplett, sometimes called “autism’s first child.”
  • When was he diagnosed?
    His case was formally described in 1943, marking the first widely recognized, clinical diagnosis of autism as a distinct condition.
  • Who diagnosed him?
    Dr. Leo Kanner, a psychiatrist at Johns Hopkins Hospital in Baltimore.
  • Why is this important?
    Kanner’s 1943 paper, built around Donald’s case, effectively introduced “infantile autism” as a separate diagnosis in modern psychiatry.

A bit of historical nuance

  • People with what we would now call autism almost certainly existed long before 1943; they simply were not labeled with this diagnosis at the time.
  • Earlier psychiatrists used terms like “childhood schizophrenia,” “mental deficiency,” or vague descriptions of “withdrawn” children, so Donald Triplett is considered the first formally diagnosed under the new concept of “autistic disturbances.”
  • Kanner had observed Donald in person as early as 1938, but it was only after he collected 11 similar cases that he defined autism as its own diagnostic category in 1943.

Tiny timeline snapshot

  1. 1933 – Donald Triplett is born in Forest, Mississippi.
  1. 1937–1938 – His parents seek help for his unusual development; he is briefly placed in an institution and later examined by Leo Kanner at Johns Hopkins.
  1. 1943 – Kanner publishes his paper describing 11 children, with Donald as “Case 1,” establishing the first clear medical description of autism.

So, when you ask “when was the first person diagnosed with autism,” the historically accepted answer is: 1943, with Donald Triplett’s formal diagnosis and description by Leo Kanner.

TL;DR: The first formally diagnosed person with autism was Donald Triplett, whose case was published by Leo Kanner in 1943, even though autistic people undoubtedly existed long before that date.

Information gathered from public forums or data available on the internet and portrayed here.