insomnia
"This has been very helpful for me.  My sleeping pattern has been messed up for years since having a daughter with a significant disability which included among many other things a sleeping disorder. Ambien has enabled me to fall asleep consistently after a short period of time trying to fall asleep whereas I used to more often than not lay awake for hours before falling asleep.  It is interesting for me that there has been a couple of times where I was not able to go to bed for over an hour after taking it and it didn't seem to make me feel any more groggy or sleepy, but when I did finally go to bed, I fell right asleep."