Remote diagnosing is a controversial practice among psychologists. But for a while now, many in the field have been concerned about US President Donald Trump's seemingly dire mental state. In February last year, a letter written by 33 psychiatrists and psychologists was published in The New York Times. They warned of the risks the US president poses. In "The Dangerous Case of Donald Trump", a book published in October, 27 psychiatrists and mental health experts describe the president's severe personality disorder. The most frequent diagnosis in the book is narcissistic personality disorder.

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Bärbel Wardetzki is a psychotherapist in Germany who has written several books about narcissism. In an interview with DW, she explains what narcissism is.

DW: Am I a narcissist if I like myself?

Bärbel Wardetzki: No, the term narcissism is not easy to define. I see narcissism as a way of dealing with the world. It ranges from positive narcissism to pathological narcissism. People who say "I like myself" simply have high self-esteem. They do not experience self-doubt but they are still able to structure their inner life, help and comfort themselves. They are aware of their capabilities and limits. Actually, many people view this attitude as negative narcissism but it is actually positive. A narcissistic personality disorder is characterized by a deeply disturbed sense of self-esteem that is compensated for by creating a larger-than-life image of oneself.

What about negative narcissism? Does US President Donald Trump suffer from a narcissistic personality disorder?

It is difficult to diagnose Trump as I do not actually know him and can only interpret his behavior. Maybe he suffers from a completely different personality disorder but the narcissistic aspect is what catches the eye. He's a prime example of narcissism. His behavior and way of dealing with others by simply dividing the world into good and evil is typical of this disorder.

What type of behavior do psychologists associate with a narcissistic personality disorder?

There are several criteria that must be met before one can speak of a disorder. Criticism is met with anger as it is associated with shame and humiliation. People with this disorder are manipulative. Relationships with others are exploited for personal gain. Another factor is overblown self-esteem. The person feels unique and great. Those who have a personality disorder constantly fantasize about infinite success, power, beauty, brilliance and idealized love. They make great demands on themselves and others. They constantly expect attention and admiration. Furthermore, narcissists lack empathy. This point however, is a topic of contention at the moment. People with a personality disorder can show empathy but not in the sense of compassion, which means feeling for others. Last but not least, people with a narcissistic personality disorder are extremely envious of others.

You say that a narcissistic personality disorder is based on low self-esteem. So if Trump brags about having a bigger nuclear button than Kim Jong Un, does he actually fear having a smaller one?

Exactly. "I am not good enough" is the underlying fear in this disorder and it can be an existential fear. People who develop narcissistic structures often do not even know who they are. They have often been manipulated as children who had to live up to a specific image. They draw their self-esteem from external accomplishments: power, big cars or important positions. But all this conceals an emotionally neglected child who was never given the attention it actually needed.

What's the best way to deal with a narcissist like Trump?

Well, that's the million dollar question. When dealing with people like that, your own self-esteem is challenged. After all, they can quickly make you feel worthless and miserable and no longer the person you are. It is important to learn to take a stand against them, to raise your voice and not be intimidated. And to leave when the relationship becomes too destructive. Which, unfortunately, we cannot do in this case.

Bärbel Wardetzski is a psychotherapist and the author of the book "Narzissmus, Verführung und Macht in Politik und Gesellschaft" ("Narcissism, seduction and power in politics and society")

The interview was conducted by Julia Vergin.