In writing the application form for a MSc course from a British university, I came across the following session:

Disability/Special Needs

Please tick the box next to the statement which is most appropriate to you.

(0) You do not have a disability nor are aware of any additional support requirments in study or accomodation.
[...]
(6)You have mental health difficulties
(7)You have an unseen disability, eg diabetes, epilepsy, asthma
(8)You have two or more of the above disabilities[...]
(9)You have a disability not listed above
Please specify:
I have been diagnosed as having ADD and was said as said as mildly autistic; but I have been functioning pretty well in Hong Kong, a place of no support at all. Does that mean I have to tick 0?

i would say it depends on whether you feel you will need accomodations or not. if you think you might need help at some point, i would check off box 9; you might not need the help at first, but maybe later, and noone says you have to accept all the help offered.

just my thought.