Abraham Lieberman
Adolf Hitler had Parkinson Disease. Although it affected him physically, it is unclear if it affected his ability to analyze, to conceptualize, to reason, or to think. Although it cannot be proven if he was cognitively impaired or a drug induced psychosis (a psychosis induced by the amphetamines he received as a treatment for his Parkinson disease) the evidence suggests he was not seriously cognitively impaired and that any unrealistic thinking resulting from amphetamines was, probably, a minor factor.
Hitler was a life-long risk-taker, a gambler. His life-long risk- taking, his high stakes gambling, antedated his development of Parkinson disease and his use of amphetamines. His life-long risk-taking, his high stakes gambling is considered to be the reason he made startling (and favorable) decisions before World War II and the reason he made similarly favorable decisions early in World War II. His risk taking and high stakes gambling is also the reason he made startling bad decisions: decisions that ultimately led to Germany losing World War II.
Adolf Hitler had Parkinson disease (PD). This is not in dispute: it has been documented in descriptions by his contemporaries including physicians. It has been documented by comparing samples of his handwriting from before he was diagnosed in 1934, to shortly before he killed himself in 1945. It has been documented by videos taken over his lifetime. There is a dispute as to whether Adolf Hitler had post-encephalitic or idiopathic PD. This cannot be resolved. However, it does not affect whether PD affected Hitler’s conduct: The effects of the disease, not its cause are in dispute.