We tried Melatonin, which worked somewhat, herbal teas, etc. This progressed for a couple of years until she was diagnosed with depression/anxiety. In hind site she says that her sleep issues started at the same time as her depression. After she was put on Zoloft sleep hasn't been an issue.

I'm not sure if the sleep issues led to the depression, or if it was a symptom. Either way, keep an eye out for depression.