A study has suggested that Parkinson's disease was a factor in the poor decisions Hitler made towards the end of the Second World War.
And Hitler's personality and love of violence may have been shaped by the condition, health experts have claimed.
A team from the University of Pittsburgh have published a study exploring how Parkinson's affected "Hitler's personality and influenced his decision-making", reports the Daily Mirror.
The effects of his illness may even have prompted military mistakes such as his assault on Russia in 1941, a massive miscalculation which played a huge role in Germany's World War II defeat.
"It is believed that Adolf Hitler suffered from... Parkinson's disease throughout his life," the researchers wrote.
"Germany's defeat in World War II was influenced by Hitler's questionable and risky decision-making and his inhumane and callous personality, both of which were likely affected by his Parkinson's condition.
Crystal meth addiction
HIstorians and doctors alike have tried to explain Hitler's thirst for violent conflict, with previous research backing the Parkinson's claim.
According to a US intelligence report released last year, he may also have been battling a crystal meth addiction during the war.
The Pittsburgh research said: "Hitler often accused, deceived, and betrayed others for personal gain and was especially known for his lack of remorse and sympathy, which can be further associated with his Parkinson's.
"The character traits which define Hitler as a notorious political leader and brutal dictator, one who carried out innumerous war crimes in the 20th century, may then be directly associated with his diagnosis."