Even if we quibble about Mr. Trump's narcissism, we can be certain that he has ADHD, because the criteria for this condition are based solely on observable behavioral symptoms. If we don't recognize his ADHD (the distractibility, the trouble with sustained attention, the easy boredom, the impulsive, thoughtless comments) we can't understand the man, because narcissism doesn't explain any of these. Narcissism alone would not account for such astounding ignorance about matters of state - if narcissism was his only pattern he would have feared being exposed as a fraud by his lack of knowledge. And the ignorance and impulsivity stemming from his ADHD make his narcissism far more unpredictable and dangerous.

https://dockruse.medium.com/ignoring-trumps-adhd-doesn-t-help-him-or-us-5ce95754dcf0

https://www.amazon.com/Recognizing-Adult-ADHD-Attention-Hyperactivity/dp/1949642224