Sleep is the natural and periodic state of rest that all the animals go through. Sleeping habits are different in different parts of the world. These differences are visible between the cultures where artificial light is used and the ones where it is not common.
Research indicates that cultures with less artificial light (mostly in the old days) have broken-up sleep patterns. Thus, people tend to sleep in periods, waking up after every few hours depending on various things. However, it has been proven that light plays a crucial role in the way people wake up after sleeping. Apparently, sleep patterns have changed after the inception of the artificial light, with people generally sleeping for solid hours and waking up after a constant amount of sleep, as opposed to waking up after short spans of time.
Researchers are still investigating as to how the bright light is able to overcome depression, in addition to resetting a sleep cycle. One theory is that an area of the brain, near the visual pathway, responds to light by sending out a signal to suppress the secretion of a hormone called melatonin. This hormone, according to a proof, is able to induce sleep when the drive to sleep is not sufficient, and is able to inhibit the drive for wakefulness; thus, playing a role in how people sleep and wake up.
While earlier research indicated the visual pathways and the regulation of melatonin as a reason for this change in the sleep cycle, more recent researches have shown that if one applies bright light to the back of the knee, it may cause a shift in a the daily sleep-wake schedule. This revelation has suggested that the blood stream also has an effect on the biological clock, along with the neurons found in the visual cortex.
Light may also help the mood of a person when he/she wakes up, specifically when suffering from certain disorders. Seasonal Affective Disorder (SAD), is a good example of such an adversity. More commonly identified as the winter blues, it is a mood disorder which some people, who may have absolutely normal mental health in all other circumstances and throughout most of the year, face in cold weather. Sometimes, this phenomenon is also observed in other seasons, but is quite rare. Normally, this condition occurs repeatedly on an annual basis.
One of the side effects of this disorder is abnormal sleep patterns, and one of the effective methods of treating it has been light therapy. This involves very bright light bulbs being used to illuminate an area where the subject is asked to sit.
When a person is asleep and the curtains are sharply drawn to reveal intense sunlight, he/she is usually woken up harshly. The sunlight definitely affects the person, causing the eyelids to flicker open. A person woken up in such a way would most probably be irritated.
Lately, many products in the market include lamps with light that increases the intensity gradually, so that a person wakes up slowly and is not exposed to severely intense light all of a sudden. Most people would find the latter option more pleasant, and would prefer it to intense light. Therefore, it is obvious that light plays a role in the wake up patterns of the up.
