Now to get back to the actual question from the OP:
We use it with our DS who is 4.5 and has sensory processing disorder, and possibly generalized anxiety disorder and odd (too young for a diagnosis).
We only give him 1mg bc that's we're we were told to start and it was effective at that dose. He went from screaming and throwing major tantrums at bedtime to cooperating with the bedtime routine and then falling asleep in his bed alone. He does still wake up a couple times at night and we don't give him anymore, so we're working on helping him stay calm in his bed so he can return to sleep.