The effect of insomnia definitions, terminology, and classifications on clinical practice.
There is a need for newer, more clinically useful classifications for insomnia. Identification of specific subtypes of insomnia helps anchor research, allows for prediction of prognosis/course of the condition, and may allow for individualization of treatment. Existing classifications differ, and many terms remain inadequately defined, which leads to diagnostic confusion. Historically, insomnia has been classified according to symptom type, symptom duration, and underlying cause, but these classifications have not been based on evidence of their utility, and newer research suggests the need for change. Symptoms may include difficulty falling asleep, trouble staying asleep, and not feeling restored by sleep, although it has not been clear that it is possible to identify distinct subtypes of patients by symptom or that distinguishing symptom type affects the course of clinical treatment. Classification of insomnia by duration most commonly involves three categories: transient (no more than a few days), short-term (up to 3 weeks), and long-term (more than 3 weeks). This categorization is of uncertain utility and has been primarily based on nonempiric concerns about treatment with sedative-hypnotic medications for periods longer than several weeks. The subtyping of insomnia in terms of whether there is an identifiable underlying cause such as a psychiatric or medical illness was based on an unproven assumption that in most instances other disorders caused insomnia. Recent studies suggest the need to revisit these classification strategies. Evidence that symptom types typically overlap and change over time complicates the categorization of subjects by whether they have difficulty falling asleep or staying asleep or have nonrestorative sleep. New studies of the treatment of chronic insomnia change the perspective on duration of treatment and, as a result, classification of duration of disease. Two studies of nightly pharmacotherapy for insomnia including more than 800 insomnia patients have not identified any increase in the risks after 3 to 4 weeks of treatment. In addition, nonpharmacological treatments demonstrate long-lasting efficacy in patients with chronic insomnia, and the development of abbreviated cognitive-behavioral therapies, which are particularly well suited to primary care practice, have improved their applicability. Newer studies of the relationships between insomnia and associated medical and psychiatric conditions undermine the notion that insomnia is always a symptom and caused by an underlying condition. They suggest that, although it is important to identify and treat these conditions, this may not be sufficient to alleviate the insomnia, which may adversely affect the course of the associated disorder. As a result, treatment targeted specifically to the insomnia should be considered. All of these developments point to an increasing ability to tailor therapy to the particular needs of patients and to optimize the clinical management of insomnia.
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