Donald Trump is not the first president to be called unhinged, by political enemies and medical professionals alike. But some of his predecessors were manic depressives, bipolar and even psychopathic, say experts.
In the summer of 1776, the American Revolutionary War was going so badly for the rebels that George Washington apparently attempted suicide by redcoat.
As his militiamen fled in panic at Kip's Bay, Manhattan, the 44-year-old supreme commander lapsed into a catatonic state, according to biographer Ron Chernow.
Washington just sat on horseback staring into space as dozens of British soldiers charged at him across a cornfield.
The future first US president's aides grabbed the reins of his mount and with some difficulty managed to spirit him to safety.
One of his generals, Nathanael Greene, later said the Virginian was "so vexed at the infamous conduct of his troops that he sought death rather than life".
Washington's suspected emotional breakdown illustrates how even the greatest of crisis leaders can snap under pressure.
Fast forward nearly two-and-a-half centuries, and the mental state of his political descendant is under somewhat less forgiving examination.
Presidential psychiatry has been all the rage ever since Donald Trump entered the White House.
There's even a publishing subgenre devoted to putting the 45th president on the shrink's couch.
Such titles include The Dangerous Case of Donald Trump: 27 Psychiatrists and Mental Health Experts Assess a President, Rocket Man: Nuclear Madness and the Mind of Donald Trump, A Clear and Present Danger: Narcissism in the Era of Donald Trump, and Twilight of American Sanity: A Psychiatrist Analyzes the Age of Trump.
But Mr Trump - who maintains he is "a very stable genius" - is by no means the first US leader to find himself depicted as a lunatic.
John Adams, the second president, was described by arch-rival Jefferson as "sometimes absolutely mad".
The Philadelphia Aurora, a mouthpiece of Jefferson's party, assailed Adams as "a man divested of his senses".
Theodore Roosevelt, the contemporary Journal of Abnormal Psychology theorised, would "go down in history as one of the most illustrious psychological examples of the distortion of conscious mental processes".
While Roosevelt campaigned in 1912 to return to the presidency, prominent US historian Henry Adams said: "His mind has gone to pieces… his neurosis may end in a nervous collapse, or acute mania."
After Woodrow Wilson had a stroke, his critics claimed the White House had become an insane asylum, pointing out the bars installed on some first-floor windows of the executive mansion.
But as John Milton Cooper recounts in his Wilson biography, those bars had in fact been fitted during Teddy Roosevelt's presidency to keep his young sons from breaking windows with their baseballs.
And yet, according to a psychiatric analysis of the first 37 commanders-in-chief, Adams, Roosevelt and Wilson did have actual mental health issues.
The 2006 study estimated that 49% of presidents suffered from a malady of the mind at some stage in their life (a figure said by the researchers to be in line with national rates).
Twenty-seven per cent of them were found to be affected while in office.
Coolidge ordered a servant to rub a rag in the fireplace ashes, climb a step ladder and dab it on the painting to darken Adams' head.
(John Quincy Adams also suffered from depression and used to mope around the White House, playing billiards and irritating his British-born wife, according to a biography by Harlow Giles Unger.)
Coolidge all but withdrew from political life. Most concerning was his ignorance about economic alarm bells a year before the 1929 Wall Street Crash.
As legislation was considered to rein in rampant stock speculation, he told reporters: "I don't know what it is or what its provisions are or what the discussion has been."
In his autobiography, the 30th president wrote: "When he [my son] went, the power and glory of the presidency went with him.
"I do not know why such a price was exacted for occupying the White House."
Other presidents were able to bounce back from the personal Gethsemane of bereavement.
Theodore Roosevelt battled severe depression early in his political career after the death of his young wife and mother on Valentine's Day, 1884.
He rode off for a couple of years to the Badlands of Dakota territory, where he built a ranch, hunted buffalo, arrested thieves and knocked out a gunslinger in a saloon.
"Black care really sits behind a rider whose pace is fast enough," he said.
Abraham Lincoln was prone throughout his life to melancholy, according to biographer David Herbert Donald.
In 1841 in Springfield, Illinois, while serving as a state legislator, Abe broke off his engagement to Mary Todd (they eventually wed) and plunged into deep depression.
A friend put him on suicide watch, removing razors and knives from his room.
It was rumoured in the state capital that he had gone crazy.
Given his morose disposition, aides must have feared how he would cope during the American Civil War with the death of his 11-year-old son, Willie, probably from typhoid fever, at the White House in February 1862.
Later that year, after another humiliating defeat, this time at the Second Battle of Bull Run, Lincoln told his cabinet he felt almost ready to hang himself, according to Donald's book.
But despite his grief, the 16th president managed to hold himself together and the union, too.
It was only after Willie's death that Lincoln finally fired his vacillating military commander, George McLellan.
He replaced him with a depressive, shy, probable alcoholic who was squeamish at the sight of blood: Ulysses Grant would lead the Union Army to victory.
Despite the enduring stigma of mental illness, some experts believe it may help certain leaders - up to a point.
A 2012 study by psychologists from Emory University in Georgia found several presidents exhibited psychopathic traits, including Bill Clinton.
The two determined to be most psychopathic were Lyndon Baines Johnson and Andrew Jackson, Mr Trump's hero.
Psychopathic attributes were identified by the Emory team as superficial charm, egocentricity, dishonesty, callousness, risk-taking, poor impulse control and fearlessness.
The research covered every president except the current one and Barack Obama.
Professor Scott Lilienfeld, who led the study, says: "I suspect that in the long run these traits are going to catch up with people.
"So yes, they might allow people to rise to positions of leadership.
"I'm less confident they're going to result in better overall leadership, especially in the long term."
LBJ, for example, had an ego the size of his home state of Texas.
He brazenly stole his 1948 Senate election, then even more shamelessly joked about it, according to Robert Caro's multi-volume biography.
Johnson thought nothing of casually putting his hand up another woman's skirt while his wife, Lady Bird, was sitting right next to him.
He liked to humiliate underlings by summoning them to take dictation while he urinated in a washbasin or defecated in a toilet.
However, the seeds of LBJ's political Alamo may have been sown in his widely suspected lies to the American people about a fake naval skirmish in the Gulf of Tonkin in 1964.
Johnson used the incident to dramatically escalate the US war in Vietnam.
But amid the ensuing hecatomb of the Tet Offensive four years later, LBJ announced he would not run for a second term.
Andrew Jackson - who signed the ethnic-cleansing Indian Removal Act - is remembered today more for his cruelty than for the enviable accomplishment of being the only president ever to fully pay off the national debt.
And Bill Clinton's reputation, of course, was left in tatters by his sexual impulsivity.
Some presidents have handled the strains of the Oval Office less well than others.
Even as vice-president, Richard Nixon was taking prescription drugs for anxiety and depression, along with sleeping pills washed down by alcohol.
John A Farrell's biography details how the unstable Watergate leader drank excessively throughout his turbulent tenure.
White House tapes record him slurring his words amid the tinkle of ice cubes.
Henry Kissinger, his top diplomat, once said Nixon couldn't take a call from the British prime minister during a Middle East crisis because he was "loaded".
His psychotherapist, Dr Arnold Hutschnecker, was the only mental health professional ever known to have treated a president at the White House.
He said Nixon had "a good portion of neurotic symptoms".
And so, is Donald Trump mentally ill?
Prof Davidson's armchair diagnosis is no. He cites debate among psychiatrists internationally as to whether narcissism - a trait so often attributed to the current president - is even a bona fide personality disorder.
But Nassir Ghaemi - author of A First-Rate Madness: Uncovering the Links Between Leadership and Mental Illness - believes President Trump has "classic manic symptoms".
The professor of psychiatry at Tufts University School of Medicine in Boston says: "He doesn't sleep much at all. He has a very high physical energy level.
"He's very impulsive with spending, sexually impulsive, he can't concentrate.
"His traits were most beneficial for him during the presidential campaign, where he was extremely creative.
"He was able to pick up on things that normal, mentally healthy, stable persons, like Hillary Clinton, for instance, did not."
The Trump presidency, we are so often told, has shattered historic norms.
But the strange and troubled lives of previous commanders-in-chief seem to raise the question, what is normal?