Disney's definition is vague, but deliberately so: DAS is meant for those with a disability that prevents them from being able to wait for extended periods (again, not defined, which is frustrating, although I'd suggest anything approaching 30 minutes or more counts) in a traditional queue. It's an individualized determination, and the focus is on the nature and severity of the person's symptoms with respect to "tolerating extended waits" standing in a traditional line, rather than on any particular diagnosis or disorder. Whether that definition applies to your child is ultimately up to you, your son, and his doctor -- Disney isn't going to ask for medical proof, although you'll need to go through the prescribed registration process.