The issue of whether Donald Trump is mentally unfit to be president — or, to put it more bluntly, whether he suffers from a serious mental disorder — isn’t one to be taken lightly, yet it sometimes seems destined to be tinged with comedy. In 2017, when speculation about Trump’s mental state was first reaching full boil, Allen Frances, the psychiatrist who wrote the criteria that defines narcissistic personality disorder, published a righteous letter in The New York Times insisting that Trump was not an example of that syndrome. I looked up the criteria on several prominent medical websites, and guess what? Trump meets every one of the criteria. (Don’t take my word for it; look it up yourself. That letter to the editor read like Freud coming back from the dead to insist that the Woody Allen character from the ’70s was not, in fact, neurotic.) Trump is the kind of screw-loose blowhard who has inspired all too many of us to play armchair psychiatrist. We’ve been putting him on the couch for the entire run of his presidency. So most, if not all, of the insights presented by the upcoming documentary “#Unfit: The Psychology of Donald Trump” (it drops on Aug. 28) will be familiar to any student of TISDS (Trump Is Seriously Deranged Syndrome). Trump, as Dan Partland’s film explains, is a malignant narcissist. (Has there ever been a DSM diagnosis that sounded like more of a direct insult?) The film details the four qualities in Trump that define that syndrome: his paranoia (the feeling that any journalist who asks him a challenging question, or any staff member who doesn’t kiss his ring, is out to get him); his anti-social personality disorder (the constant lying, the lack of remorse about even the most destructive things he does); the sadism (the thousands of vicious attacks and insults in his tweets); and…well, the narcissism (do I need to detail that?). In addition, the film analyzes his propensity to create and live in his own reality. It explores his absence of empathy — which, of course, is the defining quality of the sociopath. (They’re not insane; they just don’t care about you — or anyone else.) And it compares him to Hitler and Mussolini, and to the authoritarian leaders of our own time. As headlines, most of these insights may sound like very familiar news. Yet “#Unfit” finds freshly perceptive nuances within them. Rick Reilly, the veteran sports writer and author of “Commander in Cheat: How Golf Explains Trump,” says that Trump is “among our best golfing presidents,” and so he asks a question: Why would Trump need to cheat at golf? But cheat he does. According to Reilly, Trump jerry-rigs his golf cart to go twice as fast as any of the others, so that he can, if he chooses, be the first to the tee and more able to manipulate the results. He’ll plant his mark in the wrong place, or deny he hit a ball into a lake. He’s claimed championship wins when he lost, or where he was the only player. And then there’s this: He tried to cheat Tiger Woods. No one says the well-being of America is riding on Trump’s sleaziness on the green. Yet the film suggests that if Trump will cheat at golf, he’ll cheat at anything. From the start, the psychoanalyzing of Trump has been fraught with controversy, much of it stemming from the Goldwater Rule. In 1964, Fact magazine published a survey of 1,189 psychiatrists saying that Barry Goldwater was unfit to be president. Goldwater sued and won, and according to the psychologist John Gartner he was right to win. The original article featured such diagnostic tidbits as “He has never forgiven his father for being a Jew” and “He is a mass murderer at heart.” In other words: pure outrageous speculation. The guiding principle that emerged from this was that psychiatrists shouldn’t offer diagnoses of public figures they haven’t personally analyzed. But Gartner, in the documentary, claims that the Goldwater Rule was never intended to be a gag order. It was a way of steering the psychiatric establishment away from unfounded speculation. There’s a less famous guideline, known as the Tarasoff Rule, which imposes a duty on the part of psychiatrists to warn appropriate persons when a patient may present a risk of harm. The Tarasoff case, from 1969, concerned a patient who told a psychiatrist that he was going to kill his girlfriend. No warning occurred, and he went home and committed that very act. It is now a law in all 50 states that if a psychiatrist is aware of a potential danger, confidentiality goes out the window. Gartner claims that in the case of Trump, this absolutely applies. “If we didn’t speak up,” says Gartner, “that would be the immorality.” He goes on to offer a fascinating rebuke to the Goldwater Rule — namely, that the DSM manuals are based on observable behavior, which Trump has provided an abundance of. He may be the most observed president in history. But if a psychiatrist conducts a personal interview with, say, a sociopath, it’s in their very nature to lie about themselves. So given the gravity of the current moment, why shouldn’t psychiatrists speak out? The movie points out that certain mental illnesses shouldn’t disqualify one from the presidency. Abraham Lincoln famously suffered from depression, and the malady may actually have helped him win the Civil War. “It was baked into who he was,” says Gartner, “and so the enormous burden of the Civil War was actually something he was able to endure.” But malignant narcissism is, in a word, malignant. The film interprets Trump’s attacks on the media — his attacks on facts, on reality itself — as a form of gaslighting, because they become a way of deliberately distorting the public’s sense of what is real and what is not. And Lance Dodes, a psychiatrist in the film, discusses how Trump’s lack of loyalty — all the people he has turned on and fired — is a direct reflection of his zeroing out of empathy. He has no human connections. “It flips from ‘You are the greatest person’ to ‘You are a horrible person, you are a worthless person, I will attack you, I will destroy you’.”