From time to time, most people find themselves muttering (or screaming) at 4:00 a.m., “why can’t I sleep?!” For some, difficulty falling asleep or staying asleep can even become the norm. This is called insomnia — upsetting, disruptive, and a way of life for some. Insomnia can include trouble falling asleep, trouble staying asleep, or not getting restful sleep at least three nights per week. (Trouble falling asleep is defined here as taking more than 30 minutes to fall asleep. Trouble staying asleep is defined as being awake for more than 30 minutes during the night.)