It’s a rule that the American Psychiatric Association came up with after an embarrassing incident involving Barry Goldwater, who was the republican who ran for president in1964.
Barry Goldwater was running against Lyndon Johnson in 1964. Before the election, a liberal publication called Fact magazine conducted a poll of psychiatrists, and published an outrageously biased story that said that psychiatrists believed that Goldwater was mentally unfit to be President. (“1,189 Psychiatrists Say that Goldwater is Psychologically Unfit to be President.”) Goldwater lost the election in a landslide — losing to Lyndon Johnson.
Incidentally, LBJ supporters had a slogan about Goldwater: “In your guts, you know he’s nuts.” — pretty clever!
The problem was that the survey the article was based on was laughably unscientific, and in hindsight it was obvious that the whole thing was unfair. (15k psychiatrists got the survey in the mail, less than 20% responded. (2.5k) responded, about half didn’t like Goldwater. 1/4 said he was okay, and about 1/4 said they didn’t know enough about the man to have an opinion. The magazine printed a wildly biased story that left out all of the context and just printed a few of the very negative commnets that some of the psychiatrists had. Since there were 15,000 psychiatrists who got the survey, of course a few of them really disliked Goldwater and had some very damaging opinions about him. And the article made it sound like psychiatrists in general hated Goldwater.
The American Psychiatric Association was upset that psychiatry was sort of manipulated for political propaganda, and wanted to encourage its members to not do that anymore. So, in 1973, the American Psychiatric Association passed a rule to discourage psychiatrists from participating in that sort of nonsense. They call it the “Goldwater Rule.”