According to DSM-5, individuals with Narcissistic Personality Disorder NPD have at least five, or all of the symptoms listed below
Grandiosity with expectations of superior treatment by others.
Fixated on fantasies of power, success, intelligence, attractiveness, etc.
Self-perception of being unique, superior, and associated with high-status people and institutions.
Needing constant admiration from others.
Sense of entitlement to special treatment and to obedience from others.
Exploitative of others to achieve personal gain.
Unwilling to empathize with others' feelings, wishes, or needs.
Intensely jealous of others and the belief that others are equally jealous of them.
Pompous and arrogant demeanor.
Can a Narcissist Function as a U.S. President?
It is, perhaps, no surprise that widely held impressions about Trump's narcissism are corroborated by the DSM criteria. The key question to ask is whether, having come so far despite his psychiatric disorder, Trump or any other narcissistic personality can communicate well enough to be an effective leader of the free world.
There have been many narcissistic heads of state before but the clearest examples, such as Fidel Castro, Saddam Hussein, and Hugo Chavez, have been dictators.
Narcissists are difficult to deal with, whether as friends or as politicians. They do not feel the need to build consensus, which is why most are screened out by democratic systems of government.