The debate around Donald Trump’s mental health and his fitness to continue as US president rages on. Most recently Prof Allen Frances, the psychiatrist who wrote the book (or at least the diagnostic criteria) on narcissistic personality disorder has penned a letter to the New York Times stating that although Trump is a “world-class narcissist” he does not have a mental illness as he suffers no personal distress or impairment from his condition, which is a prerequisite for the diagnosis.

In the other camp, an American psychologist who believes Trump is a “malignant narcissist” has started a petition to remove him from office and a group of mental health professionals including psychiatrists have stated that his instability makes him incapable of serving safely as president. In doing so, these psychiatrists have broken the much-cited Goldwater rule which prohibits American psychiatrists from commenting professionally on public figures without conducting a formal assessment, declaring it to be unethical to stay silent in the face of what they consider to be dangerous pathology.

The ethics of psychiatric diagnosis-from-afar are complex; psychiatrists have a duty to protect the public as well as the individual, which could be highly pertinent if the US president, a man with access to the nuclear codes, is making decisions in a state of mental ill health. On the other hand, psychiatry has a shameful history of being used to silence and oppress for political purpose and we run the risk of inadvertently stigmatising those who have a mental illness by association with a bigoted authoritarian like Trump. So we should indeed exercise caution.

Being a psychiatrist, I conduct psychiatric assessments daily and know how valuable they are. We perform a detailed clinical interview and record a specific set of observations known as a mental state examination. We familiarise ourselves with any available medical records and seek out other sources of information (speaking to relatives for example) to fill in the gaps. Collating the information gathered from this exercise and mining it for signs and symptoms of mental illness allows us to arrive at a diagnosis.

‘We have certainly had more than enough opportunity to observe Mr Trump, so are we in a position to offer a diagnosis?’ Photograph: Alamy

One might argue that although no formal psychiatric assessment has been conducted on the president, our subject has lived most of his life in the public eye and we have a wealth of information on him, especially since the election campaign. Observation over a period of time can in fact be one of the most informative methods of assessing for a mental illness. When a patient presents in distress and with an unclear diagnosis, admission to a psychiatric ward and close observation can often give the answer more convincingly than a formal assessment interview. We have certainly had more than enough opportunity to observe Trump, so are we in a position to offer a diagnosis?

Making a formal diagnosis without an assessment would be misguided, but in some situations, I imagine psychiatrists would be obliged to make their concerns about a politician’s mental health known. If a public official was displaying clear signs of a serious mental illness such as psychosis and had not received the necessary help, psychiatrists should notify the relevant authorities for the sake of the individual as well as the public, so an assessment can be conducted. However, that is not the situation we are in and irrespective of the ethics of their assertions, those who believe that Trump has a mental illness are wrong for the clinical reasons outlined by Frances.

Trump does have multiple narcissistic traits, he simply does not qualify for a diagnosis of the personality disorder

Trump does indeed have multiple narcissistic traits – the grandiose sense of self importance; the preoccupation with power, success and beauty; the need for admiration and the sense of entitlement – but without distress or impairment he simply does not qualify for a diagnosis of the personality disorder. Furthermore, the speculative diagnosis of malignant narcissism – said to include aspects of narcissism, sadism, psychopathy and aggression – is not recognised in either of the two major diagnostic manuals used by psychiatrists around the world, so should be disregarded. No “alternative diagnoses” allowed.

Although we should lay the possibility of Trump having a mental illness to rest and accept that efforts to depose him are better focused on other avenues such as peaceful protest, legal challenge and the hope of eventual impeachment, a psychiatric perspective may still be useful in helping us to make sense of his personality. A plethora of descriptions has been used already, but viewing him through the lens of his personality traits might help us to predict his behaviour and develop strategies to counter his actions.

Trump’s wealth has undoubtedly helped him to meet the expectations of his own grandiose self-image throughout his life, and the hate speech he has used to appeal to the disaffected American masses has been a key tool in helping him to attain his immense newly found power. These behaviours have allowed him to fulfil his narcissistic fantasies and in doing so, avoid distress and impairment. Shocking executive orders serve the purpose of his chief strategist Steve Bannon’s racist agenda, but they also keep him continuously in the news cycle and the subject of conversation. His behaviour will continue in this vein as narcissists need a constant stream of attention and admiration (“the narcissistic supply”).

Beneath narcissism festers a deep-seated sense of inadequacy; it is a defence mechanism designed to protect against the painful reality of a narcissist’s belief in their own inferiority. They possess a fragile ego vulnerable to any threat of revealing this imperfection and the associated humiliation, known as a “narcissistic injury”. That is why the suggestion that his inauguration was poorly attended was such a slight to Trump. That is why he shamelessly self-promotes while derogating his detractors with a vigour rarely seen in politics.

Perhaps Trump’s bigotry is also derived from his narcissism; since he must see himself as perfect to defend his fragile ego, he may also see his own characteristics (white, male, heterosexual, Christian) as superior. He is likely to do what he can to ensure those who share these characteristics remain superior by proliferating inequality and disadvantage for those who do not. In his mind, since the US has now become an extension of himself, he will act to enhance its position as the dominant power, irrespective of the cost to the rest of the world.

Declaring Trump mentally ill and calling for his removal may be erroneous and unethical, but we must not close the door on understanding his thinking and predicting his behaviour by shutting down the discourse around his personality.