Insomnia is a type of sleep disorder that people have when they cannot fall asleep, or they have trouble staying asleep the whole night. Most of the insomnia cases are related to depression, stress, poor sleeping habits, anxiety, lack of exercise, certain medications, or chronic illness. According to the National Sleep Foundation of the United States, people who have insomnia may feel dissatisfied with their sleep and generally have one or more of the following symptoms along with insomnia: low energy, fatigue, mood disturbances, difficulty concentration, or decreased performance at office or school.