My sister's daughter has Autism.
My sister used a leash, sometimes when my neice was younger, to control her daughter when they went out places. Although it was kind of fruitless in a lot of ways and my neice is getting older so it's not really prevalent anymore.
Anyway, she also has a tag on the leash from a doctor to show it is for medical reasons.
She has been considering getting her a dog helper now that shes older.
It's hard to explain beyond that unless you know what a kid with autism can be like when they go crazy.
Do not say " Go Crazy" That is the worse way to put it.
id say thats the right way to say it. They do go crazy. My daughter has bipolar manic depressive disorder. She definitely would go crazy sometimes. Shes on medication now and 99% of the time shes good though.