A doctor I know has been saying he thought Trump's verbiage and behavior were signs of dementia. Who can know that but the Washington Post had an interesting article stoking one's thought about it.
https://www.washingtonpost.com/opinions/after-a-brain-injury-i-suddenly-displayed-some-behavior-similar-to-donald-trumps/2016/08/05/c8bbbc12-5b55-11e6-831d-0324760ca856_story.html?hpid=hp_no-name_opinion-card-a%3Ahomepage%2Fstory
