On March 6 1854, when Robert Schumann first became a patient at a private sanatorium located in Endenich (now part of Bonn), he assumed that entering as a voluntary patient would count in his favour when he eventually decided to leave. Instead, he would spend the rest of his life there.
Already famous for his prowess as a pianist and a composer, Schumann's seemingly idyllic life, including his marriage to Clara and the eight children they had together, was marred by his lifelong problems with depression. By late 1853, he began developing new and even more worrisome symptoms, including auditory hallucinations of angelic voices (which may have been linked to problems with tinnitus). This soon progressed to his experiencing visions of angels and, as his condition deteriorated, of demons as well. The demonic voices continually told him he was a sinner and that they would be throwing him into Hell. He also screamed at times due to the belief that he was being savagely attacked by wild animals. 
In the first months of 1854, he began worrying about the possibility of harming himself or his family and he warned Clara that he posed a danger to her.n On February 27, he eluded the family members keeping watch on him and proceeded to a bridge overlooking the Rhine river near his Dusseldorf home. Then, after throwing his wedding ring into the river, he jumped in himself. Fortunately, two fisherman witnessed his jump and managed to reach him in their boat and bring him to safety (despite his attempting to throw himself into the river a second time).
When the fishermen brought Schumann home, he was placed under the constant care of two physicians (Clara didn't learn about the suicide attempt until some time later). After being kept in isolation for several days, he asked his doctors to arrange his transfer to a mental institution "because only there would he recover." Since the Schumanns were relatively well-off, the decision was made to send him to the private sanatorium at Endenich where he would receive far better treatment than in a public hospital. Though Clara was distraught by her husband's condition, she was helped by her mother, children, and family friend, Johannes Brahms, all of whom were present when he was transferred to Edenich with only one physician to accompany him.
The asylum at Edenich certainly had a good reputation and its director, Dr. Franz Richarz, was considered one of the top experts in his field. Located on a seven-acre estate which had originally been built as a summer residence, it had been purchased just two years before by Dr. Richarz who had then converted it to a hospital. Retaining much of its original splendor, including extensive gardens, the hospital seemed like an ideal setting for recovering patients. Certainly its policies were unusually progressive for that era with patients being allowed to walk on and off the grounds for exercise (though Schumann was constantly supervised due to his suicidal history). Unfortunately, treatment was also extremely expensive and, despite offers of help from Brahms and other friends, was a major financial concern for Clara Schumann.
She was also concerned about the weekly reports she received from the hospital about her husband. The doctors had asked her not to visit or communicate with her husband directly since they thought this would help him recover faster. Even the few visitors he received weren't allowed to talk to him, only to observe from a distance. Whether or not this made good medical sense, it certainly contributed to his feeling of isolation, especially from Clara and his beloved children.
While the doctors continued to report on his progress, any hope for a speedy recovery was dashed by Robert's frequent relapses, not to mention his constant guilt over something that happened prior to his marriage to Clara (historians are divided over what exactly this was). Despite his relapses, he definitely improved over time and often went on walks through the hospital's gardens. Though he was eventually allowed visitors, his improvement was still rocky.
The hallucinations slowly subsided but he was still prone to paranoid delusions, including the belief that his wine was poisoned. He was also distressed over not hearing from Clara at all and he apparently didn't realize that the doctors had instructed her not to write to him directly. After a few months, the doctors relented and asked Clara to write to him but she was still asked not to discuss any topics that might distress him.
While Clara tried to write as often as possible, her own life was going through a profound change. While she had largely been overshadowed by her husband before his hospitalization, raising her children alone allowed her to establish herself as one of Europe's finest pianists. As a result, she was kept busy going on frequent musical tours to help pay for Robert's care as well as to support herself and her children. Despite her worries about Robert's condition, she definitely enjoyed all the public attention she was receiving and, ironically enough, her success as a pianist allowed her to earn far more money than Robert would likely have earned at his regular music position in Dusseldorf.
As for Robert himself, he continued to recover and, while his letters to Clara were sporadic, he also wrote to many of his other friends, including Brahms. In these letters, along with what he told friends during visits, Robert seemed apprehensive about his doctors and the treatment he was receiving at Endenich. When one of his close friends, Joseph Joachim, visited Schumann December, 1844, Robert told him that he wanted to leave Edenich because "the doctors there completely misunderstood him". There was no evidence that Joachim told Clara about this but Robert later sent her a letter in which he wrote, "My Clara, ” he wrote, “I feel as if something dreadful lies before me. What sorrow—if I never see you and the children again!” Though his doctors took this to mean that he was considering suicide, it seems more likely that he was afraid that he would never be allowed to rejoin his family.
Though Clara herself didn't visit Edenich, she arranged for several friends to see her husband and investigate other possible clinics. One friend, Bettina von Arnim, visited Robert and later told Clara that she would do everything she could "to free poor Schumann as soon as possible from his imprisonment." She was also extremely critical of the hospital and the doctors themselves, many of whom she thought were even more disturbed than their patients.
Despite Bettina's urging, Clara was reluctant to take her husband out of the hospital and, instead, met with Dr. Richarz who assured her that everything was fine and that Robert should not be moved. This was apparently enough for Clara and she agreed to keep him at Edenich for at least another year. Unfortunately, Robert had apparently regarded Bettina as being his last hope and his condition quickly deteriorated when nothing changed.
By 1856, he had become much worse as Brahms noted in his two visits that year. After one of these visits, Brahms reported that Robert was largely incoherent and that "often he only babbled, something like bababa—dadada" and that he showed little sign of understanding his friend when he tried to talk.
In June of that year, Clara received a telegram from Edenich while she was touring in England. The telegram said that Robert was "totally debilitated" though he was still apparently conscious. She finally went to Edenich herself on July 27 after receiving word that her husband was dying. Even though Brahms and the doctors had tried to stop the visit (to spare her the shock), Clara was still stunned by what she saw. As she would later report, "He smiled at me and, with great exertion placed his arm around me. I will never forget it...He spoke with spirits, so it seemed, and would not permit anyone around him for long, or he would become restless. It was nearly impossible to understand him any longer."
Robert Schumann died in his sleep on July 29 at 4 pm. Clara came to his bedside a half-hour later to see her husband one last time. "I stood by the corpse of my dearly beloved husband and was at peace; all feelings went in thanks to God that he was finally free." The funeral was held just four days later and the general consensus among everyone present was a sense of relief that his "miserable existence" was over. Clara Schumann never remarried and spent the rest of her life as a concert pianist who helped to popularize Schumann's work worldwide.
As for the exact cause of Schumann's death, that continues to be a mystery even today. While h was only forty-six when he died, the autopsy report itself was largely inconclusive. In an article Doctor Richarz wrote on Schuman in 1873, he claimed that Robert suffered from "incomplete general paralysis" resulting from a "slow, but irreversible and progressive deterioration in organization and strength of the entire nervous system." Along with his "melancholic depression", Richarz attributed Schumann's early death to his refusal to eat and the emaciated state of his body when he died.
Other medical historians have also suggested that Schumann suffered from schizophrenia or bipolar depression based on the bizarre symptoms he often displayed. In recent years, another explanation that seems more widely accepted was that he suffered from tertiary syphilis (also called general paresis in those days). Certainly he had numerous symptoms linked to advanced syphilis, including hallucinations, speech and movement difficulties, and an eventual mental collapse. Schumann himself apparently believed that he had syphilis due to a previous affair (which contributed to his delusios of being sent to Hell due to his "wickedness"). Still, no traces of the brain degeneration commonly seen in tertiary syphilis turned up in his autopsy, something that would have been evident if he really had the disease. Certainly there was no indication that he passed it on to Clara or that any of his children developed congenital syphilis afterward (though one son was committed to a psychiatric asylum years later).
Ironically, it may well have been the treatment received at Edenich that truly led to Schumann's death. In his own article, Doctor Richarz displayed a total lack of empathy towards his patient that reflects Schumann's own sense of despair at not being allowed to leave the hospital and rejoining his beloved wife and children. Though he had recovered significantly between 1854 and 1855, his plea that he be allowed to return home was largely ignored by his friends and family. Though his hopes were raised by visits from friends such as Bettina von Arnim, his condition only deteriorated when he felt abandoned and he began starving himself as a result. As it happens, other patients also engaged in hunger strikes, largely in protest to the treatment they were receiving at Edenich, though little is known about what later happened to them.
So, was Robert Schumann's death due due to despair at being abandoned or because of a still-undiagnosed medical condition? We may never know for sure. Despite the mystery surrounding Schumann's death, the love affair between Clara and Robert, as well as their friendship with Brahms continues to be commemorated. With numerous books and movies written about the three of them, not to mention the musical works that Johannes Brahms and Robert Schumann completed between them, has become the stuff of legend.