The mental stability of U.S. President Donald Trump has become a long-standing issue that started even before he has taken over the highest seat in the country. Psychologists and psychiatrists agree that the real-estate-magnate-turned-politician satisfies the Diagnostic and Statistical Manual (DSM) for narcissistic personality disorder.

However, one of the most eminent psychiatrists in the world begs to differ.

Dr. Allen Frances, professor emeritus of psychiatry and behavioral sciences at Duke University Medical College, noted that Trump's world-class narcissistic tendencies do not make him mentally ill.

A patient must be first suffering from distress and impairment before being diagnosed with mental disorder. Surprisingly, Trump is not experiencing distress and impairment. Instead, he is the one causing severe distress to others.

"Most amateur diagnosticians have mislabeled President Trump with the diagnosis of narcissistic personality disorder," Frances, who chaired the task force that wrote DSM IV, wrote in a letter to New York Times. "I wrote the criteria that define this disorder, and Mr. Trump doesn't meet them."

Read: More Than Half of Americans Are Stressed Out Due to Politics

In addition to his narcissistic tendencies, some psychiatrists publicly diagnosed Trump with mental illness due to his bad behavior. However, Frances noted in his letter that "bad behavior is rarely a sign of mental illness and the mentally ill behave badly on rarely." Due to this, lumping Donald Trump with those who have mental illness will be a "stigmatizing insult" to them.

In his letter, Frances also expressed his concern over what he called "psychiatric name-calling." Psychiatrists are supposed to be bound by the Goldwater Rule, which is added in the American Psychiatric Association's code of ethics in 1973. Under the rule, psychiatrists are not allowed to diagnosed public figures at a distance or they have not personally examined.

Psychiatrists have been trying to prove that Trump is unfit and incapable of running the country on psychiatric grounds. However, Dr. Frances advised his fellow psychiatrists and colleagues to denounced Trump for his "ignorance, incompetence, impulsivity and pursuit of dictatorial powers."