In the western world, there are several people affected by chronic insomnia. Numerous studies estimate that 30% to 40% of the general population is affected at some time in their lives with a form of insomnia that goes on for several months, and about one third of those are described as severely affected. Daytime symptoms of insomnia include tiredness, lack of energy, difficulty concentrating and irritability. Recent epidemiologic research focusing on the quality of life has identified significant insomnia-related morbidities that relate to work productivity, health care utilization, and risk of depression. Insomnia is associated with diminished work output, absenteeism, and greater rates of accidents.