History shows that he was most certainly OCD - with compulsions about cleanliness, work performance and other things. He even couldn't have his fingernails cut at the end it's said. Very odd fellow.
Was he ADHD? Not much has been said on that. Maybe - he was considered a rogue thinker with radical and even extreme thoughts. He would many times go off on a tangent and without regard for his financial or personal safety.
An interesting idea.
If I recall he lived quite a few of the last years of his life in a hotel suite in Las Vegas, completely ignoring all personal hygeine - no haircuts, bathing, fingernails and eating only some kind of favorite cake with his rotted teeth.