He surmised that hypnosis could be used to treat hysteria.

Hippolyte Bernheim (1840 – 1919) was a French physician and neurologist, born at Mülhausen, Alsace. He received his education in his native town and at the University of Strasbourg, where he was graduated as doctor of medicine in 1867. The same year he became a lecturer at the university and established himself as a physician in the city.
When, in 1871, after the Franco-Prussian war, Strasbourg passed to Germany, Bernheim moved to Nancy (where he met and later collaborated with Dr. Ambroise-Auguste Liébeault), in the university of which town he became clinical professor.
When the medical faculty took up hypnotism, about 1880, Bernheim was very enthusiastic, and soon became one of the leaders of the investigation. He became a well-known authority in this new field of medicine.
Bernheim believed that Charcot's provocation of hysteria during hypnosis came about from suggestions given at that time - hence the hysteria was induced via suggestion not heredity. He also took Charcot's studies forward a bit and believed that hypnosis could be used therapeutically. He even surmised that hypnosis could be used to even treat hysteria.