Sleep regulation and insomnia

For years, the subject of sleep failed to generate much interest from either the field of medicine or that of psychology – a curious fact, as a 60-year-old has spent some 20 years out of those 60 sleeping. In fact, up until the age of approximately 3 years, a child spends more time asleep than awake. It would be an extraordinary evolutionary oversight if this phenomenon of sleep, which is seen in virtually all organisms, did not have an important and vital function (McNamara, Evolution of sleep phylogenetic and functional perspectives. Cambridge University Press, Cambridge, 2009). The consequences of sleep deprivation make themselves known by interfering with our emotional and cognitive functioning on the following day, when one may also experience the imperative nature of sleep, sometimes at very inconvenient moments (Cluydts, Sleep Med Rev 7(4):293–295, 2003).