My 3 yr old son was just diagnosed with PDD-NOS...HE SCREAMS NON STOP!!! I think it may be his was of stimming idk...has anyone ever heard of that or have similar children with stimming? He just screams when he excited, sad, whenever, happy...its just all the time!! Drives me nuts:) Its usually just short little screams highpitched, but its all the time..we say "Tasker be quiet and stop screaming" and he'll stop for like a min and go again!!