Sleep problems due to a chronic illness. My better half works rotating shifts and takes it with Melatonin to help deal with the sleep problems that causes.
As to the poster that says it doesn't cross the blood/brain barrier and that it can't be useful ingesting it, I'd ask why it has made a huge difference in our sleep and why it is used not only for improving sleep, but also for anxiety attacks? It works great for both and that is through taking it by tablet, or sublingually as it is also available?