Article continues below advertisementA psychologist is certain Donald Trump has dementia after evaluating and comparing recent changes in the president's health.During a guest appearance on "The Daily Beast Podcast," Dr. John Gartner claimed Trump's "clear" signs of "deterioration" are proof the 79-year-old is battling dementia.Trump has been hit with accusations his cognitive capabilities are declining for months - well before he was inaugurated as the 47th president of the United States back in January.