Anna O.

Anna O. was the pseudonym of a patient of Josef Breuer, who published her case study in his book Studies on Hysteria, written in collaboration with Sigmund Freud. Her real name was Bertha Pappenheim (1859–1936), an Austrian-Jewish feminist and the founder of the Jüdischer Frauenbund (League of Jewish Women).

Anna O. was treated by Breuer for severe cough, paralysis of the extremities on the right side of her body, and disturbances of vision, hearing, and speech, as well as hallucination and loss of consciousness. She was diagnosed with hysteria. Freud implies that her illness was a result of the resentment felt over her father's real and physical illness that later led to his death.

Her treatment is regarded as marking the beginning of psychoanalysis. Breuer observed that whilst she experienced 'absences' (a change of personality accompanied by confusion), she would mutter words or phrases to herself. In inducing her to a state of hypnosis, Breuer found that these words were "profoundly melancholy fantasies...sometimes characterized by poetic beauty". Free association came into being after Anna/Bertha decided (with Breuer's input) to end her hypnosis sessions and merely talk to Breuer, saying anything that came into her mind. She called this method of communication "chimney sweeping", and this served as the beginning of free association.