Insomnia is the body's way of saying that something isn't right. Things that may cause insomnia include stress, too much caffeine, depression, changes in work shifts, and pain from medical problems, such as arthritis.
Many people have insomnia. People who have insomnia may not be able to fall asleep. They may wake up during the night and not be able to fall back asleep, or they may wake up too early in the morning.