Insomnia is a symptom which can accompany several sleep, medical and psychiatric disorders, characterized by persistent difficulty falling asleep and/or difficulty staying asleep. Insomnia is typically followed by functional impairment while awake.
Both organic and non-organic insomnia without other causes constitutes a sleep disorder, primary insomnia. One definition of insomnia is “difficulties initiating and/or maintaining sleep, or non-restorative sleep, associated with impairments of daytime functioning or marked distress for more than 1 month.
According to the United States Department of Health and Human Services in the year 2007, approximately 64 million Americans regularly suffer from insomnia each year. Insomnia is 41% more common in women than in men.