In 1895 Viennese physicians Joseph Breuer and Sigmund Freud published Studien über Hysterie. This work, which provided the first detailed account of the free-association method, is customarily regarded as the starting-point of psychoanalysis. Joseph Breuer had discovered the "cathartic" method of curing hysteria in the early 1880s while treating the patient who would later be immortalized as "Anna O."; this patient, who exhibited a myriad of severe hysterical symptoms, found that the symptoms would disappear when she told Breuer the details of their onset. (Freud's biographer, the pioneering psychoanalyst Ernest Jones, gives "Anna O.," whose real name was Bertha Pappenheim, a large share of the credit for inventing what she called the "talking cure.")
Freud learned of this interesting case from Breuer shortly after its termination in June 1882. The case made a strong impression on him, and a few years later he began using a combination of hypnosis and the cathartic method in his own neurological practice. From this Freud gradually developed the method of free association, in which the patient was encouraged to say whatever came into his/her mind however "nonsensical" or "irrelevant," since Freud believed that the patient's statements provided clues about the network of associations already established in the mind, and would thus lead the therapist to the source of the patient's neurosis. "It was through devising the new method that Freud was enabled to penetrate into the previously unknown realm of the unconscious proper and to make the profound discoveries with which his name is imperishably associated" (Jones, Sigmund Freud I, 265).
Hook & Norman, The Haskell F. Norman Library of Science and Medicine (1991) F26.