Insomnia is a sleep disorder. Those who are affected by insomnia struggle either to fall asleep or to remain asleep throughout the night, or both. When they wake up from their sleep, they do not report feeling refreshed. Insomnia is frequently accompanied by symptoms such as drowsiness during the day, low levels of energy, irritability, and a depressed mood. It may lead to difficulties focusing and learning, as well as an increased risk of being involved in an accident involving a motor vehicle.  There are two different types of insomnia: short-term insomnia, which can last for days or weeks, and long-term insomnia, which can last for more than a month.