A brief encounter with a Jewish prostitute might have led Hitler to orchestrate the genocidal Holocaust, according to a new study by psychiatrists.
Hitler might have contracted syphilis, which, possibly untreated, led to his madness and eventually targeting of the Jews and the mentally retarded.
There is "ample circumstantial evidence" for the theory, according to psychiatrist Dr Bassem Habeeb.
Dr Habeeb said that there had been speculation that Hitler had syphilis from diary entries made by his personal doctor, Theo Morrell.
"If Hitler's life is looked at through the lens of a syphilis diagnosis, one clue leads to another until a pattern of infection and progressive infection emerges, a disease that may have defined him from youth as an outsider and that progressively ravaged his body and mind," said Dr. Habeeb.
Yet despite significant medical and political clues, the theory has never been rigorously examined, he said.
The disease would have fuelled a "deadly logic and blueprint for the Holocaust" which focused on particular minorities, he added.
Hitler, who reportedly had sex with a Jewish prostitute in Vienna in 1908, put syphilis high on his political agenda, devoting 13 pages to the disease in his book Mein Kampf.
The job of "combating syphilis - the Jewish disease - should be the task of the entire German nation," he wrote, adding, "The health of the nation will be regained only by eliminating the Jews."
According to Dr. Habeeb, "Hitler's bizarre belief that syphilis was a hereditary disease that was originated and propagated by the Jews and resulted in insanity and mental retardation" could be the reason he attempted to eliminate the mentally retarded.
He said well-documented aspects of Hitler's behaviour and health such as mood swings, paranoid rages, rashes and stomach problems were typical of syphilis.
Incidentally, in his diary, Dr Morrell also noted Hitler's severe gastric crises, skin lesions, Parkinson's disease and violent mood swings as evidence that he had syphilis.
Together with "sudden criminal behaviour, paranoia, grandiosity and mania", these are characteristic of cases of the advanced stage, neuro-syphilis, Dr Morrell wrote in his diary.
Dr Habeeb, who works at Hollins Park Hospital, Warrington, said though experts had previously explored the possibility that Hitler had syphilis, this was the first time that he and his team have put together the chain of secondary neuro-symptoms that meant the Holocaust became the focus of Hitler's psychotic behaviour.
"This disease can send you mad and it could be a horrible explanation for the obsession that led to the Holocaust. It's very hard to say with certainty. There's ample circumstantial evidence, though no final proof, that he definitely had it," said Dr Habeeb.
"But many other historical figures in the 19th and early 20th century suffered from syphilis without the murderous consequences wreaked by Hitler," the Daily Mail quoted him as saying.
Dr Habeeb presented his findings at the Royal College of Psychiatrists' annual meeting in Edinburgh, Scotland.