There's evidence that politicians as a group are more likely to be narcissists than the average person, but that doesn't make it ethical to apply that diagnosis — or any psychiatric label — to a specific candidate without an in-person assessment.
So argues Robert Klitzman, a professor of psychiatry and bioethics at Columbia University, in The New York Times today. He cites the American Psychiatric Association's "Goldwater Rule," which holds that "it is unethical for a psychiatrist to offer a professional opinion unless he or she has conducted an examination and has been granted proper authorization for such a statement."
The rule was implemented following Barry Goldwater's 1964 campaign, during which Fact Magazine published an article entitled "1,189 Psychiatrists say Goldwater is Psychologically Unfit to be President." The piece described the candidate as "unbalanced," "paranoid," insufficiently manly, and more. Goldwater launched a libel suit and won, though he still lost the presidency.
Today, Klitzman says, the same principle still applies, no matter how tempting it is to offer a remote diagnosis of someone like Donald Trump. Furthermore, he writes, "Doctors who loosely and freely offer diagnoses for individuals they have never interviewed threaten to make these terms cheap and ubiquitous, fueling misperceptions." Bonnie Kristian