Updated at 5:15 p.m. ET on September 13, 2024
Tuesday’s presidential debate was, among other things, an excellent real-world test of the candidates’ cognitive fitness—and any fair-minded mental-health expert would be very worried about Donald Trump’s performance.
The former president has repeatedly bragged over the past several years that he has passed various mental-status exams with flying colors. Most of these tests are designed to detect fairly serious cognitive dysfunction, and as such, they are quite easy to pass: They ask simple questions such as “What is the date?” and challenge participants to spell world backwards or write any complete sentence. By contrast, a 90-minute debate that involves unknown questions and unanticipated rebuttals requires candidates to think on their feet. It is a much more demanding and representative test of cognitive health than a simple mental-status exam you take in a doctor’s office. Specifically, the debate serves as an evaluation of the candidates’ mental flexibility under pressure—their capacity to deal with uncertainty and the unforeseen.
Just to be clear: Although I am a psychiatrist, I am not offering any specific medical diagnoses for any public figure. I have never met or examined either candidate. But I watched the debate with particular attention to the candidates’ vocabulary, verbal and logical coherence, and ability to adapt to new topics—all signs of a healthy brain. Although Kamala Harris certainly exhibited some rigidity and repetition, her speech remained within the normal realm for politicians, who have a reputation for harping on their favorite talking points. By contrast, Donald Trump’s expressions of those tendencies were alarming. He displayed some striking, if familiar, patterns that are commonly seen among people in cognitive decline.
Much of the time, following Trump’s train of thought was difficult, if not impossible. In response to a question from the moderator David Muir about whether he regretted anything he’d done during the January 6 insurrection, Trump said:
I have said “blood bash—bath.” It was a different term, and it was a term that related to energy, because they have destroyed our energy business. That was where bloodbath was. Also, on Charlottesville, that story has been, as you would say, debunked. Laura Ingraham, Sean Hannity, Jesse—all of these people, they covered it. If they go an extra sentence, they will see it was perfect. It was debunked in almost every newspaper. But they still bring it up, just like they bring 2025 up. They bring all of this stuff up. I ask you this: You talk about the Capitol. Why are we allowing these millions of people to come through on the southern border? How come she’s not doing anything—and I’ll tell you what I would do. And I would be very proud to do it.
Evading the question is an age-old debate-winning tactic. But Trump’s response seems to go beyond evasion. It is both tangential, in that it is completely irrelevant to the question, and circumstantial, in that it is rambling and never gets to a point. Circumstantial and tangential speech can indicate a fundamental problem with an underlying cognitive process, such as logical and goal-oriented thinking. Did Trump realize that his answer was neither germane to the question nor logical?
Eleven days before the debate, at a campaign event in Pennsylvania, Trump responded to criticism of his rambling speech by claiming that it is part of a deliberate strategy to frustrate his opponents. “I do the weave,” he told the audience. “You know what the weave is? I’ll talk about, like, nine different things that they all come back brilliantly together. And it’s like—and friends of mine that are, like, English professors, they say: ‘It’s the most brilliant thing I’ve ever seen.’” Viewers can judge for themselves whether the disjointed statements they heard during the debate cohered brilliantly in the end.
[Read: How swing voters reacted to the Trump-Harris debate]
The speech Trump excuses as the “weave” is one of many tics that are starting to look less strategic and more uncontrollable. Last week, David A. Graham wrote in The Atlantic that the former president has a penchant for describing objects and events as being “like nobody has ever seen before.” At the debate, true to form, Trump repeatedly fell back on the superlative. Of the economy under his presidency: “Nobody’s ever seen anything like it.” Of inflation under the Biden administration: “I’ve never seen a worse period of time.” Of the U.S. withdrawal from Afghanistan: “That was one of the most incompetently handled situations anybody has ever seen.” Harris, for her part, also showed some verbal tics and leaned on tired formulations. For instance, she invited viewers more than 15 times to “understand” things. But Trump’s turns of phrase are so disjointed, so unusual, and so frequently uttered that they’re difficult to pass off as normal speech.
Trump’s speech during the debate was repetitive not only in form but also in content. Politicians regularly return during debates to their strongest topics—that’s just good strategy. Harris twice mentioned Project 2025, which voters widely disapproved of in recent polling, and insisted three times that Americans want to “move forward” or “chart a new way forward.” Trump likewise expounded at every opportunity on immigration, a weak issue for Harris. But plenty of the former president’s repetitions seemed compulsive, not strategic. After praising the Hungarian strongman Viktor Orbán, Trump spoke unprompted, at length, and without clarity about gas pipelines in the United States and Europe, an issue unlikely to connect with many voters. A few minutes later, he brought up the pipelines again. The moderators cut him off for a commercial break. Even in cases where Trump could have reasonably defended himself, he was unable to articulate basic exculpatory evidence. When Harris raised his infamous “very fine people on both sides” remark regarding the 2017 white-supremacist march in Charlottesville, Virginia, Trump could have pointed out that even at the time, he had specified, “I’m not talking about the neo-Nazis and the white nationalists—because they should be condemned totally.” But he did not.
[Read: The mistake that could cost Trump the election]
In psychiatry, the tendency to conspicuously and rigidly repeat a thought beyond the point of relevance, called “perseveration,” is known to be correlated with a variety of clinical disorders, including those involving a loss of cognitive reserve. People tend to stick to familiar topics over and over when they experience an impairment in cognitive functioning—for instance, in short-term memory. Short-term memory is essentially your mental sketch pad: how many different thoughts you can juggle in your mind, keep track of, and use at the same time. Given the complexity of being president, short-term memory is a vital skill.
If a patient presented to me with the verbal incoherence, tangential thinking, and repetitive speech that Trump now regularly demonstrates, I would almost certainly refer them for a rigorous neuropsychiatric evaluation to rule out a cognitive illness. A condition such as vascular dementia or Alzheimer’s disease would not be out of the ordinary for a 78-year-old. Only careful medical examination can establish whether someone indeed has a diagnosable illness—simply observing Trump, or anyone else, from afar is not enough. For those who do have such diseases or conditions, several treatments and services exist to help them and their loved ones cope with their decline. But that does not mean any of them would be qualified to serve as commander in chief.
Due to an editing error, this article originally used an incorrect term for “perseveration.”