psȳkhōsis

Greek psȳkhē named the animating principle of living creatures — what departed the body at death, what the gods breathed in at birth. It was soul, mind, and life-force together, not cleanly distinguished. The -osis suffix named a condition or process: fibrosis is a fibrous condition, neurosis is a nervous condition, psychosis is a condition of the psȳkhē.

Ernst von Feuchtersleben coined psychosis in 1845 to distinguish severe mental disorders — those involving a break from reality — from neurosis, which described milder conditions. The distinction was clinical: neurosis left the patient in contact with reality; psychosis did not. This break from shared perception became the defining feature.

20th-century psychiatry debated whether psychosis was a discrete disease category or a spectrum. Eugen Bleuler coined schizophrenia in 1911, carving a specific syndrome from the broader category. The antipsychotic drugs discovered in the 1950s (chlorpromazine, first used in 1952) provided the first effective pharmacological treatment — and paradoxically confirmed that psychosis had biological dimensions.

Today psychosis is understood as a symptom that can appear in multiple conditions — schizophrenia, bipolar disorder, severe depression, substance intoxication, neurological disease. It describes hallucinations, delusions, and disorganized thinking. The Greek psȳkhē — the breath of life — is still in the word: psychosis is what happens when that animating principle turns against its owner.