got curious and took this from reddit
Depends on which version.
The recent film version fits the criteria for psychopathy and narcissistic personality disorder, as well as pseudobulbar affect due to brain injury.
https://pubmed.ncbi.nlm.nih.gov/33407973/
Heath Ledgers stands apart having a super low arousal response, but in many ways, is the most rational of all Jokers. Hes an empiricist and a sociopath, but hes lucid and knows right from wrong.
https://www.fandom.com/articles/psychology-joker-dark-knight-2008-batman
Mark Hamills Joker (my favorite) is a very realistic mentally ill person. He exhibits an attachment disorder with Batman and Harley Quinn. Bipolar, antisocial personality disorder, and borderline personality disorder.
https://www.fandom.com/articles/psychology-joker-mark-hamill-batman-animated-series-1992
Dr. Drea has written some fairly detailed personality evaluations of The Joker in various film portrayals and they can be found on Fandom and her podcast, The Arkham Sessions.