Thus far, with insomnia, either the disease model perspective is not applicable because there is no suspicion of an abnormal bodily structure or function causing the sleep disturbance, or the insomnia is seen as a symptom of another disorder where a physical cause is suspected. The question now is whether there is a primary type of insomnia, not due to another disorder, that might be considered as its own syndrome. This idea of an independent insomnia is supported by the current major sleep nosologies, as noted in chapter 1. The DSM-IV incorporates a diagnosis called primary insomnia. The International Classification of Sleep Disorders Diagnostic and Coding Manual (ICSD) defines three categories of chronic insomnia complainers in whom an intrinsic process is assumed: psychophysiological insomnia, idiopathic insomnia, and sleep-state misperception. All four of these diagnoses inherently are syndromes, and all are rather broad in scope and inclusion. Only the diagnosis of psychophysiological insomnia presumes any pathology, in this case psychological in nature. Accordingly, those individuals meeting the rather general criteria of sleep disturbance with “somatized tension and learned sleep-preventing associations” may be considered as sharing this syndrome of conditioned arousal associated with attempts to sleep (Diagnostic Classification Steering Committee, 1990).
The general notion of insomnia has no real boundary other than the complaint of sleeplessness and, therefore, is too broad to represent a syndrome definition. However, particular populations of insomnia sufferers do share specific features of their clinical courses and patterns of sleep disturbance. In fact, it can be argued that abnormalities in physiological functioning may be causing the sleep difficulties.
Physiological processes must be presumed with patients whose circadian rhythm is disordered, as described in chapter 4, “The Dimensions of Sleep.” Objective measurements of the circadian phase, such as the timing of melatonin secretion and core body temperature, also correspond with the subjective sleepiness experience and sleep propensity. The circadian system is unusually early in those with the advanced sleep phase syndrome and is unusually late in those with the delayed sleep phase syndrome. A complete lack of entrainment with the photoperiod, as with blind free-running patients, also has a primary abnormal circadian influence. In all of these disorders, physiological variation from norms is evident, and the afflicted individuals share similar symptoms, clinical courses, and consequences. Therefore, a syndromal designation would be appropriate in these clinical situations.
Source: David N. Neubauer, “Understanding Sleeplessness: Perspectives on Insomnia,” The Johns Hopkins University Press, Baltimore 2003
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