insomnia
"I've suffered from insomnia since college and would struggle some nights to get 2 hours of sleep.  I would get tired, but as soon as I lay down to sleep, I would stare at the ceiling for hours unable to fall asleep and when I did I would not stay asleep.  My doctor prescribed me Ambien to try and help with my insomnia.  In my particular case, Ambien has worked very well.  I'll take it and within 30-40 minutes it will put me to sleep.  There are still occasional nights where I'll take Ambien and still not be able to sleep, but most of the time it works very well."