T.C.
My son is 8 and has Aspergers/ADHD. He sometimes chews on his shirt collar, but most of his nervous habits are verbal- singing and humming constantly. At school, they tried giving him a necklace called chewelry that's designed to give him something more appropriate to do. You can probably find a lot of information on these types of behaviors from web pages related to autism- they are often called "stims".