I wonder if I have this. Edit: no I don't think I do.
One of the symptoms of ADHD, as I understand it, is difficulties with symbol decoding (I think that is what it is called). I think it may be related to poor working memory. Say you want to decode a substitution cypher. With ADHD you have to keep referring back to the decoding chart more often than those without. (I took a test on this as part of my diagnosis and I sucked at it).
I think maybe that affects understanding equations with all the symbols and Greek letters and such?