Everybody needs to sleep. This is a fact that cannot be contested. Sleep slows the body down, putting every major component of the body into a more relaxed state. This is also acknowledged as a medical fact. People dream while they're asleep and, in theory, animals may also experience dream-like scenarios. Despite the fact that most people can't remember them, this too can be confirmed medically. However, aside from all of the above listed effects (and side effects), what exactly does sleeping do for a person? That is slightly less certainly known, which is probably the reason so many institutions and research programs are delving deep into the scientific facts behind sleep.

The natural growth hormones that the body needs to develop are produced in large quantities during sleep. This has often been seen as the explanation for why people who don't sleep too much often end up being slightly shorter than their peers. These hormones are produced at their peak during puberty and tend to cease production afterwards. People are still unsure why the body produces more of it during sleep. There are some that theorize that this is merely a part of the side effects of sleep, of sorts, arguing that the body is too busy coordinating itself to really produce growth hormones. However, this assumption is rather arguable because the body is still coordinating the same systems during sleeping hours as it is during the waking hours.

According to recent studies, sleep may have appreciable effects on lifespan and well-being. People who experience extreme bouts of sleep deprivation eventually suffer a degenerative state of physical health, with prolonged lack of sleep becoming lethal. It is still uncertain exactly why this is the case, though the fact that this can happen is not being disputed. Research shows that people who have been deprived of sleep for long periods of time physically wither away. According to some findings, the mind is also heavily affected, with anxiety and depression being potential effects of over-extended waking hours. This is often attributed to the disruption of the usual production and flow of the central nervous system's biochemical agents, which regulate mood and emotional stability, among other things.

The nervous system suffers from sleep deprivation as well, according to some recent findings. People who do not sleep regularly tend to have unstable moods and poor reflexes. In most cases, alertness and environmental awareness tend to be compromised, often to the point that even simple tasks can require more concentration than normal to perform properly. The part of the brain that controls reflex and motor functions is not the only part that suffers, as the areas that are believed to govern actions during social situations are also known to be compromised. Currently, there is no certainty as to just what happens during sleep that causes this, but there are several theories.

There are other sleep-related theories being tested, such as what biological purpose dreams serve, but they are considered less of a concern. Some findings even point to the possibility that the natural state of the human body (and, indeed, any animal body) is to be asleep, rather than awake. It is rather surprising that sleep, something that is so integral and critical to preserving human health, is so little understood by medical science.