Early Efforts:

Scientists first became involved in hypnosis around 1770, when Dr. Franz Mesmer started investigating an effect he called "animal magnetism" or "mesmerism" (the latter name still remaining popular today).

In the early 19th century, Abbé Faria continued the scientific study of hypnosis. Unlike Mesmer, who claimed that hypnosis was mediated by "animal magnetism", Faria claimed that it worked purely by the power of suggestion.

In the 1840s and 1850s, Carl Reichenbach began experiments to find any scientific validity to "mesmeric" energy, which he termed Odic force. Although his conclusions were quickly rejected in the scientific community, they did undermine Mesmer's claims of mind control.

James Braid:

The evolution of Mesmer's ideas and practices led James Braid (1795–1860) to coin the term and develop the procedure known as hypnosis in 1842. He rejected Mesmer's misleading idea of magnetism inducing hypnosis, and ascribed the creation of the 'mesmeric trance' to a physiological process — the prolonged attention on a bright moving object or similar object of fixation. He postulated that "protracted ocular fixation" fatigued certain parts of the brain and caused the trance, "nervous sleep." At first he called the procedure neurhypnotism but the current word soon emerged. Braid developed his ideas over time, down-playing his early idea of nervous sleep and increasing the role of psychological factors rather than fatigue. He came to recognize the role of intense, focused concentration by the participant on the hypnotist, a condition he called monoideism.

Braid attempted to use hypnotism to treat various psychological and physical conditions. He had little success, notably in his attempts to treat organic conditions. Other doctors had better results, especially in the use of hypnosis in pain control, a report in 1842 described an amputation performed on a hypnotized participant without pain. The report was widely dismissed and there was strong resistance in the medical profession to hypnotism, but other successful reports followed. Dr. James Esdaile (1805–1859) performed over 300 operations using hypnosis as pain control. The development of chemical anesthetics soon saw the replacement of hypnotism in this role.

The deaths of Braid and Esdaile curbed the interest in hypnotism. Experimentation was revived into the 1880s, mainly in continental Europe where new translations of Braid's work were circulated. The neurologist Jean Martin Charcot (1825–1893) endorsed hypnotism for the treatment of hysteria. La méthode numérique, still more popular on the continent than in England, led to a number of systematic experimental examinations of hypnosis in France, Germany, and Switzerland. The process of post-hypnotic suggestion was first described in this period. Exaggerated claims were still made, extraordinary improvements in sensory acuity and memory were reported under hypnosis.

1880s and Later:

From the 1880s the examination of hypnosis passed from medical doctors to psychologists. Charcot had led the way and his study was continued by his pupil, Pierre Janet. Janet described the theory of dissociation, the splitting of mental aspects under hypnosis (or hysteria) so skills and memory could be made inaccessible or recovered. Janet provoked interest in the subconscious and laid the framework for reintegration therapy for dissociated personalities.

Also in this period Ambroise-Auguste Liébault (founder of the Nancy School) first wrote of the necessity for cooperation between the hypnotizer and the participant, for rapport. He also emphasized, with Bernheim, the importance of suggestibility.

Sigmund Freud met with Charcot, and with Liébault and Bernheim. Back in Vienna he developed abreaction therapy using hypnosis with Josef Breuer.