Yes it is a huge issue.
We have had students who have been taking drugs for ADHD and you can expect months of delays, if it is even possible to get the medical at all. One who was a supervisor in construction working at heights and CASA said he was "Likely to take unaccceptable risks and be impulsive".
Much better if people don't get a label stuck on them and other people accept them for the amazing people they are instead of saying they are "suffering" from something and filling them with pharmaceuticals and giving them a label that can cause prejudice and make doors slam in their faces for the rest of their lives.
Instructors are given this form to fill in. Read it and weep.
Form 420 (casa.gov.au)
Anyone who has any experience with people along the spectrum (who in my experience make very good pilots indeed) will know that this really shows that the people in CASA know nothing at all about it. I have taught many students on the spectrum and IF they want to be pilots they are the complete opposite of the behaviours shown and their level of focus and attention to detail is extraordinary. However if they are being forced into flying against their will by pushy parents they may exhibit some of those behaviours, as would any student who wants to be doing something else.