Donald Trump: We warned you of the dangers of his presidency 5 years ago -- how do we stop it from happening again?

In two days, the 45th president of the United States, Donald J. Trump, will leave the White House. As specially-trained experts remove his staff's COVID cooties from the building, Joe Biden and Kamala Harris will take their oaths of office, ending what many experts believe is the worst presidency in our country's history. But America will never be the same.

Nearly 5 years ago to the day, we issued the following warning from neuroscientist Bobby Azarian, who made the case that Trump "has a mental disorder that makes him a dangerous world leader." By our estimates, more than 30 million people have read this story -- and it remains far and away the most popular story we've ever published. --Roxanne Cooper

According to a number of top U.S. psychologists, like Harvard professor and researcher Howard Gardner, Donald Trump is a "textbook" narcissist. In fact, he fits the profile so well that clinical psychologist George Simon told Vanity Fair, "He's so classic that I'm archiving video clips of him to use in workshops." This puts Trump in the same category as a number of infamous dictators like Muammar Gaddafi, Napoleon Bonaparte, and Saddam Hussein. And although there are narcissists out there who entertain us, innovate, or create great art, when a narcissist is given immense power over people's lives, they can behave much differently. As the 2016 presidential election grows nearer we must ask ourselves, if elected president would Donald Trump act on the behalf of the will of the people, or would he behave more like a dictator—silencing any dissenting voices, perpetually refusing to compromise, and being oppressive to certain groups? To answer that, we should ask a little bit more about what makes a narcissist tick, and how they tend to behave when given free rein.

What is it exactly that makes someone a certifiable narcissist and not simply a person who has a healthy amount of confidence and a burning desire to achieve great goals? According to the Mayo Clinic, narcissistic personality disorder is "a mental disorder in which people have an inflated sense of their own importance, a deep need for admiration and a lack of empathy for others."

Trump's shortage of empathy can be seen clearly by his stances on topics like immigration. Instead of recognizing that the data shows that most Mexican immigrants are not violent, but instead people simply looking for a place where actual opportunity exists, with a broad brush he claims that they are "criminals, drug dealers, rapists, etc." In a similar vein, Trump has vowed to ban all Muslims from entering the country should he be elected. It appears that his lack of empathy has distorted his mind's ability to grasp the fact that the refugees he speaks of are actually seeking safety from the same murderous maniacs that he wants to keep out. Perhaps if Trump had relatives in countries like Syria and Iraq, he might understand the constant fear that most live under, and in turn become more willing to welcome them with open arms rather than leaving them to be slaughtered.

But a lack of empathy is just one part of narcissistic personality disorder. Just beneath the surface layer of overwhelming arrogance lies a delicate self-esteem that is easily injured by any form of criticism. We have all seen Trump unjustifiably lash out at a number of people with harsh and often extremely odd personal attacks. When he thought he had been treated unfairly by Fox News host and Republican debate moderator Megyn Kelly, he responded by calling her a "bimbo" and later saying that she had "blood coming out of her eyes, blood coming out of her wherever." In response to the strange, misogynistic comments Kelly said that she "may have overestimated his anger management skills." If the news host would have pegged him as a bona fide narcissist from the beginning she might have expected such shamelessly flagrant behavior.

To be fair, it is certainly true that not all narcissists are terrible people. Some of our most beloved celebrities and musicians have been suspected narcissists, including Elvis Presley, Marlon Brando, Kanye West, and even Alec Baldwin. Not only are these decent people, some have also done a lot of good through philanthropic work. Surely Donald Trump has more in common with these individuals than he does with a psychopath like Saddam Hussein.

There is no doubt that this has been true of the past, yet there is one critical difference between those people and Trump or Saddam. Only the latter two were in or are pursuing positions as heads of state—a role that grants enormous power over world affairs and people's lives. While a narcissistic personality might be one of the traits that allowed Trump to be such a successful businessman and reality TV star, it is also the trait that makes him potentially dangerous as a political leader.

What happens when another world leader who is a loose cannon doesn't give Trump the admiration that he feels he deserves? We can be sure that notoriously anti-American dictators like Kim Jong-un of North Korea or Iran's Supreme Leader Khamenei aren't going to give him any respect, let alone praise. How would a President Trump react when he feels he is being put down or undermined? Will we see the start of World War III because the leader of the most important nation in the world doesn't feel that others are kissing his ass as much as they should be? Narcissistic personality disorder is known to have strong negative effects on relationships, and when it comes to being an effective and responsible world leader, diplomacy is everything.

If it is not clear how the promise of great power can change an essentially harmless narcissist into someone oppressive, let's see how Donald Trump's political views have changed thus far. Prior to this presidential race, most of us knew Donald Trump as a charismatic, cheeky, highly entertaining figure that seemed like anything but a bigot. Mayor Bill de Blasio of New York told CNN that the Trump he knew, and the Trump New York knew, was nothing like the intolerant xenophobe he appears to be today. It is a well-known fact that in the past Trump was a registered democrat who was in favor of liberal causes like abortion rights and pals with the Clintons. But since the promise of power has consumed him, he has become the poster boy for ultra-right wing intolerance. This change in personality and core values perfectly illustrates how the promise of power can transform narcissists. And as the race for the Republican nominee progresses, it has become increasingly obvious that Trump's yearning to rule greatly exceeds his desire to "Make America Great Again," as his slogan says.

The position of President of the United States is one that requires great empathy, a certain amount of humility, the ability to preserve relationships, and a willingness to establish new ones. These are all qualities that the narcissist lacks, and with their absence comes danger. Do we really want to put all Americans, and even the entire world, at great risk by giving a narcissist the nuclear code? Donald Trump is very much like Gollum from Lord of the Rings, and the presidency is his "one ring to rule them all." In this case we do not have the option of destroying the ring. The best we can strive for is keeping it out of the possession of those who cannot resist abusing its power.

Bobby Azarian is a neuroscientist affiliated with George Mason University and a freelance journalist. His research has been published in journals such as Cognition & Emotion and Human Brain Mapping, and he has written for The New York Times, The Atlantic, Psychology Today, and Scientific American. Follow him on Twitter @BobbyAzarian.