One of the things that we use to help our children sleep is melatonin.
Melatonin is a naturally occurring hormone that serves many purposes in the body, one of which is helping you fall asleep. It is relatively safe to use in children and has very few (if any) side effects. However, while it is available over the counter as a supplement, I would suggest talking to a medical professional before giving it to your children. That is just common sense for anything like this that you give to your children - especially the ones who can't communicate well.
With that in mind I wanted to point out some new research that appeared in the April 15th issue of the Journal of Clinical Sleep Medicine -
The Efficacy of Melatonin for Sleep Problems in Children with Autism, Fragile X Syndrome, or Autism and Fragile X Syndrome
I think this is one the first double-blind placebo controlled studies that I have seen that looks specifically at the question of how effective melatonin is in helping children with autism sleep better. The study was on the smaller side with only 12 of 18 subjects completing the study as well as being on the shorter side being only 4 weeks long. Each of the participants took either melatonin or a placebo for two weeks and then switched to the the other group.
The authors found that the group taking melatonin feel asleep faster and stayed asleep longer than the group taking a placebo.
I have not read the full study so I can't comment about why 6 children dropped out or if there were other problems with the study but I don't think the findings are all that surprising. I believe the practice of giving melatonin to children with autism to help them sleep better is fairly widespread.
The only point of contention that I have seen is how much you should be giving. In this study the dose was 3 mg but I have read other places of the range being from 1 mg up to 6 mg. We give our daughters 0.25 mg on nights they are having trouble falling asleep and that works for them.