A university professor of psychology and political science (usually in the US, a university professor has two acknowledged fields of expertise) at George Washington University (GWU) studied political leaders over a 100-year period and identified the “socio-psychological profile of disabled leaders”.  

He then defined that “disability sets in when the aides in the office stop telling them the truth about the real affairs of the world around them”. I fully agree and have since found this to be true.