To the Editor:

Fevered media speculation about Donald Trump’s psychological motivations and psychiatric diagnosis has recently encouraged mental health professionals to disregard the usual ethical constraints against diagnosing public figures at a distance. They have sponsored several petitions and a Feb. 14 letter to The New York Times suggesting that Mr. Trump is incapable, on psychiatric grounds, of serving as president.

Most amateur diagnosticians have mislabeled President Trump with the diagnosis of narcissistic personality disorder. I wrote the criteria that define this disorder, and Mr. Trump doesn’t meet them. He may be a world-class narcissist, but this doesn’t make him mentally ill, because he does not suffer from the distress and impairment required to diagnose mental disorder.

Mr. Trump causes severe distress rather than experiencing it and has been richly rewarded, rather than punished, for his grandiosity, self-absorption and lack of empathy. It is a stigmatizing insult to the mentally ill (who are mostly well behaved and well meaning) to be lumped with Mr. Trump (who is neither).

Bad behavior is rarely a sign of mental illness, and the mentally ill behave badly only rarely. Psychiatric name-calling is a misguided way of countering Mr. Trump’s attack on democracy. He can, and should, be appropriately denounced for his ignorance, incompetence, impulsivity and pursuit of dictatorial powers.