What is sleep?
All living things require sleep. It is the natural state of rest observed not only by human beings but also by other species of the animal kingdom. An adequate amount of sleep is important for one’s health and survival. It is during sleep that the body is recharged for another day of work.
Sleep has five stages. The first four stages are part of the non-rapid eye movement (non-REM) phase of sleep. The last stage is the rapid eye movement (REM) sleep. Stage one is the transition period from wake to sleep. Stage two is the intermediate level of sleep. Stages three and four are referred to as deep or slow wave sleep, with stage four as the deepest phase of sleep. The fifth stage of sleep, the REM stage, is the part of sleep where people have dreams. The term rapid eye movement was coined from the fast movement of the eyes during this phase of sleep.
Studies have been done to find a link between sleep and certain psychological conditions. It was found out that there are two sleeping difficulties that are related to psychiatric conditions. These are: