Should psychiatrists ever attempt to diagnose the psychological state of an individual with whom they have no therapeutic relationship, say, a political leader whose conduct and public utterances are a concern? 

It is a question that some will no doubt be asking again after 36 US psychiatrists and other specialists issued a statement declaring US President Donald Trump mentally unfit to serve. 

In their professional opinion, they claimed that the behaviours of Mr Trump are “tragically neither momentary lapses nor political theatre” but instead reflect a “rapidly worsening, reality-untethered, increasingly dangerous decline”.

Part of the justification for this public diagnosis is that as leader of the most powerful military machine in the world, Mr Trump has his fingers on the nuclear trigger.