WDW is consistent with the ADA (Americans with Disabilities Act).
Under the ADA, there are not any 'recognized' disabilities.
One of the points that people often forget (or maybe never knew) is that the ADA does NOT provide accomodation for
autism,
ADD,
ADHD,
asthma,
blindness,
cerebral palsy,
diabetes,
epilepsy,
paralysis,
MS
or any other condition anyone cares to name.
The ADA provides accomodation for needs related to disability (which may be due to one of the things listed above.)
Whatever condition is being referred to, some people with that conditions may have needs that are accomodated by something that everyone has access too (for example, some using touring plans, bringing GameBoys in line, using Fastpass). They would not need a GAC.
Some people with that same condition might not have their needs accomodated by those things, but might only need some slight assistance, such as being able to bring a stroller into line. They may need a GAC with a few accomodations.
Some might have more needs and require a GAC with more accomodation.
Some might have more needs, but may not have a problem with those needs at certain times (for example, during slow seasons or slow times at the park, when the wait in line might be less than 10 minutes). They may need a GAC at busier times, but not when it is quiet.
Not everyone, even with the same condition, has the same needs.
If you want more information about GAC (Guest Assistance Cards), you can find it in post #6 of the disABILITIES FAQs thread.
A GAC is not meant to shorten the wait in line, but to provide accommodation. Because how that happens varies from attraction to attraction and may even vary at the same attraction at different times on the same day, you will find that getting and using Fastpasses will give you a more consistent experience at each attraction. Using Fastpasses, you will know that you will be waiting in the Fastpass line for 5-15 minutes.
Also, even more helpful than using a GAC is to know when different parks and different areas are busy.That way, you can avoid those places and spend time in the parts of the park that are less busy. Touring plans, like Tour Guide Mike (a Theme Park Board sponsor) can help with knowing where to go to be in the less busy spots.