“Insomnia” has been used in different contexts to refer to either a symptom or a specific disorder. In this guideline, an insomnia disorder is defined as a subjective report of difficulty with sleep initiation, duration, consolidation, or quality that occurs despite adequate opportunity for sleep, and that result in some form of daytime impairment.
Except where otherwise noted, the word “insomnia” refers to an insomnia disorder in this guideline.
Insomnia disorders have been categorized in various ways in different sleep disorder classification systems. The International Classification of Sleep Disorders, 2nd Edition (ICSD-2) is used as the basis for insomnia classification in this guideline. The ICSD-2 identifies insomnia as one of eight major categories of sleep disorders and, within this group, lists twelve specific insomnia disorders.
ICSD-2 delineates both general diagnostic criteria that apply to all insomnia disorders, as well as more specific criteria for each diagnosis. Insomnia complaints may also occur in association with co-morbid disorders or other sleep disorder categories, such as sleep related breathing disorders, circadian rhythm sleep disorders, and sleep related movement disorders.
Insomnia occurs in individuals of all ages and races, and has been observed across all cultures and countries. The actual prevalence of insomnia varies according to the stringency of the definition used. Insomnia symptoms occur in approximately 33% to 50% of the adult population; insomnia symptoms with distress or impairment (i.e., general insomnia disorder) in 10% to 15%; and specific insomnia disorders in 5% to 10%.10 Consistent risk factors for insomnia include increasing age, female sex, co-morbid (medical, psychiatric, sleep, and substance use) disorders, shift work, and possibly unemployment and lower socioeconomic status. Patients with co-morbid medical and psychiatric conditions are at particularly increased risk, with psychiatric and chronic pain disorders having insomnia rates as high as 50% to 75%.
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