To the Editor:

Re “Trump Flies Into the Cuckoo’s Nest” (column, Oct. 10):

Gail Collins makes a point that we have been articulating seriously since the publication of our book, “The Dangerous Case of Donald Trump,” two years ago: President Trump is mentally unfit for office. Our publications have been derided as violations of the Goldwater Rule, “armchair psychiatry” and political bias dressed up as professional opinions.

But, as mental health professionals, we have felt a duty to address a public health crisis: a mentally unfit person in charge of the world’s most powerful military and its nuclear weapons. We have found ample evidence of his instability and grandiosity in the president’s own words and public statements, most recently confirmed in his referring to “my great and unmatched wisdom,” coupled with yet another threat to “ totally destroy and obliterate ” a foreign country.

Mr. Trump’s now familiar affinity for violence is manifest in his verbal threats and his incitement to violence at his rallies. He reacts viscerally and without reflection or consultation, now claiming “treason” and an attempted “coup.” As he confronts the humiliating prospect of impeachment, his psychological deterioration represents a clear and imminent risk.

Our observations are not “diagnosing” and do not refer to mental illness; rather, they speak to a lack of fitness that can be determined based on sufficient sources outside of a personal examination.