ADHD people are known to avoid medicine.. it's very difficult to convince them. probably they have some idealism.. consider their brains to be too great to be polluted by any kind of medicine.
another reason could be that they secretly enjoy some aspects of their brain.. like capability to argue and wind (no matter how trivial the matter at hand is).
they fail to understand what they are losing as a consequence of not treating their brain condition.
if you are not willing to take medicine, i would recommend you to listen to this lecture series by an ADHD expert- Russell A. Barkley:
as per this expert, ADD is one of the most treatable disorder! (yet only 1 in 10 ADD persons take medicine, if i remember statistics correctly)
there may be downside to taking medicines , but there are downside to not taking medicine too!!!
so one has to choose between two bad options, after deciding which one is less bad at a given point of time!
one solution could be to take the medicine off and on, on need basis...
ADD people are likely more creative, but when studying creativity doesn't help much. there are tons of things to be done in limited time- having ADD is a clear disadvantage in such a scenario, IMO.
Moreover, most of the medicines wash out of our biological system once those are stopped. So, even if somebody doesn't want to take medicine as a long term solution, he/she should consider taking it for some period.. say for a month, to see what it is like to live/learn/perform without ADD.
also check the book- 'Making a Good Brain Great' by Dr. Daniel G. Amen. It's a very good book to understand the basics of brain functioning... and to understand the cause of ADD and effect of untreated ADD.
BT