Personally I think that if there's any reason that you haven't performed as well as you could have (other than no revision etc), and has meant that you have not been in the same position as everyone else whilst taking the exam, then the exam board should be made aware. It's then down to their discretion whether they award you extra marks. I took an AS exam whilst suffering from glandular fever- had all sorts of complications which means I had literally been in bed and not eaten for around 2 weeks before the exam. Really wasn't in much of a state to be going anywhere, let alone trying to concentrate on an exam- I got a letter from the GP and my school sent it with my paper, but I'm not sure if it made any difference or not!
So, if you feel that you're at an unfair disadvantage because of a health problem, then I'd say go for it. On your list I think depression is the only thing that really fits that- most people have some degree of stress and anxiety around exam time.