Dementia praecox is a disused psychiatric diagnosis that originally designated a chronic, deteriorating psychotic disorder characterized by rapid cognitive disintegration, usually beginning in the late teens or early adulthood. Over the years, the term dementia praecox was gradually replaced by the term schizophrenia, which initially had a meaning that included what is today considered the autism spectrum.

Paul Eugen Bleuler was a Swiss psychiatrist and humanist most notable for his contributions to the understanding of mental illness. He coined several psychiatric terms including "schizophrenia", "schizoid", "autism", depth psychology and what Sigmund Freud called "Bleuler's happily chosen term ambivalence".