Sleep is a physiological state that makes us feel refreshed and energized. Insomnia is a disorder characterized by difficulty with falling asleep, staying asleep, or both. Insomnia can lower the energy level, the mood, and the work performance. The causes of insomnia can vary and are numerous: stress, medications, caffeine and caffeine-containing drinks, nicotine, alcohol, medical conditions, depression, anxiety, change in work schedule, and poor sleep habits. The list can be expanded. If you are having sleep problems start by talking to your family doctor about it.