I have ADHD (real, diagnosed ADHD, not just "I-say-I-have-ADHD-because-it's-trendy" ADHD). I have never taken the extended time exams that are offered for ADHD students, because I have never needed to, and it was diagnosed just a year ago. However, exams do stress me out and I am certain I would do better on them with some more time - but this is true for almost anyone, not just ADHD students. Thus, would it be unethical to make use of the ADHD services offered to me?
(Edit: You might ask - why would you want to / feel it is justified? Well, hypothetically say ADHD students only achieve 75% of their "non-ADHD" potential in a standard-time setting. Maybe, even though I am doing well, I would be doing even better if I did have the extended time or didn't have ADHD, i.e. due to my exhaustive preparation, even with the disadvantage of my ADHD I am still managing to get a high score. But, with a "level playing field" [extended time for me], I would be at the top of the class. However, I still don't know if this is logical / ethical.)