I have a vague recollection of reading before that Hitler might have had syphilis, but I’m not sure if I had heard of the theory that it was catching it this way which may have led to his anti-Jewish obsession:
An encounter with a Jewish prostitute in Vienna in 1908 may have given Hitler neuro-syphilis and provided the 'deadly logic and blueprint for the Holocaust' as well as giving him a reason to attempt to eliminate the mentally retarded, according to evidence presented at the Royal College of Psychiatrists.
That theory supported by 'ample circumstantial evidence though no final proof', according to a team led by Dr Bassem Habeeb…
There has been speculation that Hitler had the infection since his personal doctor, Theo Morrell expressed his own suspicion in his private diary. But the theory has never been rigorously examined, say the researchers.
'But 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.
Hitler put syphilis high on his political agenda, devoting 13 pages to the disease in Mein Kampf. The job of 'combating syphilis… the Jewish disease… should be the task of the entire German nation,' he wrote. 'The health of the nation will be regained only by eliminating the Jews'.
The theory might hold up better if it were not believed by the very nutty Dr Morell. In fact, I see from his Wikepedia entry that at least two of his treatments in 1944 may have directly sent Adolf over the edge:
Anyhow, I can see a new poster slogan for safe sex: "Avoid World War! Use a condom."
During his interrogation after the war, Morell claimed another doctor had prescribed cocaine to Hitler and at least one other doctor is known to have administered it through eyedrops after he requested it in the hours following an almost successful assassination attempt on July 20, 1944. Cocaine was routinely used for medical purposes in Germany during that time but Morell is said to have increased the dosage tenfold - despite this the concentration was still weak as the eyedrops were only 1% cocaine. Overuse of cocaine eyedrops has been associated with psychotic behavior, hypertension and other symptoms; given the weak dosage, it's more likely they were caused by Methamphetamine of which these are also common symptoms. However historians have generally tended to discount any effects of Morell's treatments on Hitler's decision-making.