So Bertha took flight, first in a fantasy world she called her "private theater" and then in illness. The first symptoms appeared in the fall of 1880, at a time when Bertha looked after her father who had fallen ill with a pleurisy that was to prove fatal. Bertha had a persistent cough and at the end of November Josef Breuer was called upon. Breuer, a well-respected internist, was the physician of the Jewish high bourgeoisie and aristocracy in Vienna. He diagnosed a hysteria, upon which Bertha took to her bed and developed "in rapid succession" an impressive array of symptoms: pain in the left side of the occiput, blurred vision, hallucinations, various contractures and anesthesias, trigeminal neuralgia, "aphasia" (from March 1881 she spoke only in English), split personality and altered states of consciousness ("absences") during which she threw tantrums that afterwards she could not remember.

Breuer, who came to see her every day, noticed that her condition was improving each time he let her tell during her "absences" the sad stories of her private theater - a process she termed (in English) "talking cure" or "chimney sweeping". However, her condition worsened after the death of her father on April 5, 1881. She refused to eat and told no more fairy tales à la Hans Christian Andersen, but instead related morbid "tragedies". She also had negative hallucinations: she didn't see the people around her and recognized only Breuer. On April 15, Breuer called upon his colleague the psychiatrist Richard von Krafft-Ebing for a second opinion. Unconvinced of the authenticity of the patient's symptoms (she claimed to ignore his presence), Krafft-Ebing blew into her face the smoke of a piece of paper that he had ignited. This caused an explosion of anger on the part of Bertha who began to beat Breuer violently. Finally, on June 7, Breuer placed her forcibly in an annex to the clinic for nervous disorders run by his friend Dr. Hermann Breslauer at Inzersdorf. There she was quieted down with the help of large doses of chloral hydrate, the sedative of choice at the time. As a result, Bertha developed an addiction to chloral.

Once the patient was stabilized (in other words: drugged), the talking cure could resume. Bertha's stories had changed. During her altered states, she no longer told imaginary tales or tragedies: "What she reported was more and more concerned with her hallucinations and, for instance, the things that had annoyed her during the past days." When she told of the frustration that had been the source of a particular symptom, it would disappear miraculously. Breuer therefore set out to eliminate one by one her countless symptoms (for example, the 303 instances of a hysterical deafness). What followed was a therapeutic marathon that resulted, if we are to believe the case history published thirteen years later by Breuer in Studies on Hysteria, in a complete recovery by June 7, 1882 (the anniversary of her admission at the Inzersdorf clinic) following a final narration during which Bertha relived a scene at the bedside of her father that was supposed to have triggered her illness: "Immediately after its reproduction, she was able to speak German. She was moreover free from the innumerable disturbances which she had previously exhibited. After this she left Vienna and travelled for a while, but it was a considerable time before she regained her balance entirely. Since then she has enjoyed complete health." Freud as well would always describe "Anna O."'s talking cure as a "great therapeutic success" (1923).

As the research of historians Henri Ellenberger and Albrecht Hirschmüller has established, the reality is quite different. Bertha Pappenheim's treatment had in fact been for Breuer a veritable "ordeal", as he wrote later to his colleague the psychiatrist August Forel. The treatment had never shown any real progress and as early as in the fall of 1881 Breuer was already thinking of placing Bertha in another clinic, the Bellevue Sanatorium run by the psychiatrist Robert Binswanger in Kreuzlingen, Switzerland. Moreover, as we know from a letter sent October 31, 1883 by Freud to his fiancée Martha Bernays, Mathilde Breuer had become jealous of her husband's interest in his flamboyant patient and rumors had begun to circulate. So when Breuer terminated the treatment in June 1882, it was not because Bertha Pappenheim had recovered (in mid-June, she was still suffering from a "slight hysterical madness"), but because he had decided to throw in the towel and transfer her to the Bellevue Sanatorium. She was admitted there on July 1, 1882 after having "travelled" briefly to visit relatives in Karlsruhe.

Founded in 1857 by Ludwig Binswanger (the grandfather of Ludwig Binswanger Jr., the promoter of existential psychoanalysis), the Bellevue Sanatorium was a renowned institution. Located in an idyllic park on Lake Constance, the sanatorium hosted with discretion and for a high fee the elite of the mentally ill. It was a place where, as the Viennese novelist Joseph Roth wrote in The Radetzky March, "spoiled lunatics from rich homes receive onerous and cautious treatment, and the staff is as caring as a midwife." There was an orangery, chaises lounges, an alley for bowl games, an outdoor kitchen, tennis courts, a room for music and another for billiard. One could also go hiking and do horseback riding nearby (Bertha took advantage of this daily). Patients stayed in comfortable villas scattered throughout the park.

Bertha Pappenheim had a two-room apartment and came with a lady companion who spoke English and French. Indeed, she was still partly "aphasic" in German and plagued by more or less the same symptoms as before. In addition to her addiction to chloral hydrate, she was now also addicted to morphine due to Breuer's efforts to calm her facial neuralgia. Her stay in Kreuzlingen lasted four months and brought little progress as far as her neuralgia and her dependence on morphine are concerned. The register at the time of Bertha's release on October 29, 1882 mentions that she was "improved", but a letter sent by her to Robert Binswanger on November 8 tells a different story: "As for my health here, I can tell you nothing which is new or favorable. You will realize that to live with a syringe always at the ready is not a situation to be envied."

Breuer declined to resume the treatment when Bertha returned to Vienna in early January 1883 after a detour by Karlsruhe. From 1883 to 1887, Bertha was readmitted three times at Dr. Breslauer clinic where she had been interned in 1881. Each time, the diagnosis by doctors was the same: "hysteria". This is confirmed by the correspondence between Freud and his fiancée Martha Bernays. Martha Bernays knew Bertha personally (Bertha's father had been her legal guardian after the death of hers) and Freud kept her informed of her friend's condition. On August 5, 1883, he wrote: "Bertha is once again in the sanatorium in Gross-Enzensdorf, I believe [Inzersdorf, in fact]. Breuer is constantly talking about her, says he wishes she were dead so that the poor woman could be free of her suffering. He says she will never be well again, that she is completely shattered." In two letters to her mother dated January and May 1887, Martha wrote as well that her friend Bertha continued to suffer from hallucinations in the evening. Thus, five years after the end of Breuer's treatment and multiple stays in clinic, Bertha Pappenheim had still not recovered.