Isolated Symptoms, Normal Variants, and Other Sleep Disorders

Abstract

Not all phenomena or symptoms that occur between falling asleep and waking up can be clearly assigned to the large group of sleep disorders, even if they have been classified in the ICSD-3 according to their predominant phenomenology. Some of them appear isolated, have no or only marginal illness significance, have been only poorly investigated, or display highly variable symptoms, so that they can neither be allocated to an existing sleep disorder nor defined as a novel sleep disorder. A sleep disorder caused by environmental influences, for example, noise, heat, or the bed partner, has to be included because the objectively present disturbing factor as well as its subjective perception may lead to insomnia, hypersomnia, or nonrestorative sleep.