ὕπνος

Hypnosis derives from Greek ὕπνος (hýpnos), meaning sleep, personified in Greek mythology as Hypnos, the twin brother of Thanatos (Death) and the son of Nyx (Night). The god Hypnos lived in a cave near the underworld through which the river Lethe flowed, breathing sleep over gods and mortals who came near. The word entered modern scientific usage through James Braid, a Scottish surgeon who coined the term 'neuro-hypnosis' (nerve-sleep) in 1841 to describe the trance state he had induced by having subjects fixate on a bright object. Braid initially believed he was studying a neurological phenomenon related to sleep; he later recognized the difference between hypnotic trance and actual sleep, attempted to rename the phenomenon 'monoideism,' but found 'hypnosis' already established and irreversible. The name stuck to the wrong concept, as names often do.

The history of hypnosis as a medical and scientific subject passes through one of the most dramatic reputational reversals in the history of Western medicine. Franz Anton Mesmer, an eighteenth-century Viennese physician, developed what he called 'animal magnetism' — a theory that the body contained a magnetic fluid whose proper flow determined health, and that illness could be treated by manipulating this fluid through the hands of a practitioner. Mesmer's treatments in Paris in the 1780s produced dramatic results: patients convulsed, wept, fell unconscious, and sometimes reported cures. A royal commission in 1784 — including Benjamin Franklin and the chemist Antoine Lavoisier — investigated Mesmer's claims and concluded that the effects were real but that animal magnetism did not exist. The effects, the commission argued, were due to imagination. This verdict effectively exiled hypnosis from respectable medicine for decades, though the clinical observations were genuine.

The clinical rehabilitation of hypnosis came through James Braid's more cautious investigations and through Jean-Martin Charcot's work at the Salpêtrière in Paris. Charcot, the most authoritative neurologist in Europe in the 1870s and 1880s, used hypnosis to study hysterical symptoms — demonstrating that paralysis, blindness, and convulsions could be produced and reversed by hypnotic suggestion. Charcot believed this demonstrated that hypnosis was a neurological state, a kind of artificial hysteria available only to hysterics. His rival Hippolyte Bernheim at Nancy argued instead that hypnosis was simply the effect of suggestion and was available to almost any subject. The Salpêtrière-Nancy debate shaped the development of both experimental psychology and the nascent psychoanalytic movement — Freud studied under both Charcot and Bernheim, and the question of suggestibility lay at the heart of his early theory of neurosis.

Modern research has neither fully vindicated nor fully debunked hypnosis as a therapeutic and investigative tool. The hypnotic state is now understood to involve a genuine alteration in attentional focus and the suspension of critical evaluation, measurable in EEG and brain imaging studies. High hypnotizability — the susceptibility to hypnotic induction — appears to be a stable, heritable trait, and the brain activity of hypnotized subjects differs from both ordinary waking and sleep. Hypnosis is used in pain management, in surgery as a supplement to pharmacological anesthesia, in psychotherapy for anxiety and trauma, and in the treatment of irritable bowel syndrome with documented efficacy. Yet its mechanisms remain incompletely understood, and its therapeutic applications remain contested because of the difficulty of distinguishing hypnotic effects from placebo and suggestion effects in clinical trials — which is, in a sense, exactly what the 1784 royal commission said.