Ancient medical books are filled with explanations of the importance of getting enough light. For example, the ancient Ayurvedic physician Charaka who lived in the sixth century B.C., recommended sunlight to treat a variety of diseases. For thousands of years people the world over have revered the sun as a great healer; some ancient cultures even worshiped the sun.
In 1980, A.J. Lewy and coworkers published an article in Science that ushered in the modern era of phototherapy. Lewy suggested that secretion of the hormone melatonin could be suppressed by exposing subjects to bright artificial light but not to light of ordinary indoor intensity. As we shall see later, melatonin is nicknamed "the chemical expression of darkness" as it is secreted at night and is believed to tell the body that it is time to sleep. It has been shown that melatonin in animals is secreted at night by the pineal gland under the influence of a circadian rhythm. Light rays impinging on the retina are converted into nerve impulses, which influence the secretion of melatonin by connections between the retina and the hypothalamus. This demonstration that one physiologic effect of light in humans, transmitted presumably via the hypothalamus, has a threshold intensity far higher than that required for vision, suggested that there might be other effects of light on the brain that require high-intensity light.
There is no doubt that the sun plays a very important role in our daily lives. During winter, the well-to-do vacations in Caribbean. The summer months are synonymous with spending time in the beach, in spite of all the warning of the potential to get skin cancer. We feel better after spending time in the sun. Today, most of the doctors and medical researchers view the sun more as a healer than a hazard.
We know that lack of sunlight can result in nutritional deficiencies. Without sunlight vitamin D cannot be metabolized in the human body, which can result in rickets. Most enzymes, hormones and vitamins need light for proper functioning. Studies have shown that different lights affect different enzymatic reactions for healing purposes. For example, one of the first test a pediatrician do to a new-born baby is to check for jaundice. If found positive, they are placed under a blue light to cure the disease. So, most of us are given light therapy, without us being aware of it.
How Does Light Affect The Human Functions?
Human beings are the product of habits and heritage. Before the advent of alarm clocks, many farmers woke up hearing the rooster crowing, announcing the arrival of morning. They milked their cows, worked in the farm and went into bed at night. There was no electricity. So, daylight announced the initiation and termination of many activities.
Modern life style differs significantly from these early days. Most of us wake up in the morning, not by hearing a rooster crow or by feeling the golden rays of sunlight slowly drifting into our rooms; we wake up by the alarm clock or by the clock radio. Many of us have tough time getting up at the first time; so we set the "snooze" button to give us a little more of precious time to sleep. The windows have heavy drapes, so most of us do not see the sunlight except when we peek outside. In the evening, many of us stay awake to watch the late night shows. (Now we have light night shows and late late night shows to keep us company till the wee hours of the night.)
The problem is that our system needs time to sleep. Studies on animals have shown that they have definite patterns they follow every day depending on the season. In autumn, most of the plants and animals get ready to go into "hibernation" for the winter period. Many birds migrate to south for the winter. During this period, they do not eat much (There is not much food to be found.) But, come spring, nature become very lively. The birds return from the south. The trees starts the new growth.
Many animals are found to time the events in their lives depending on the season, so that the functions can be accomplished at the most effective way. For example, lambs are born only in the spring when there is plentiful of food for the mother to nurse the newborn. Most of the animal species coordinate the mating time so that the birth occurs in the season when there is plenty of food available. In the tropical rainforests, birds wait till the dry season to breed. In Arctic, the breeding is timed to coincide with the melting of snow and ice.
The question is how do animals know how to predict the seasons in advance? Is it the temperature fluctuations? It cannot be, because, sometimes we have the "so called Indian Summer" in fall; but the birds do fine. It turns out that the most important factor is the day light; or more specifically the day/night cycle. Animals and plants sense the shortening of the days in the fall and perceive the arrival of winter. In spring, the lengthening of the day signifies the arrival of spring and summer. Most of the expert horticulturists know about this. They manipulate the "day light hours" (or photoperiod) to coax the poinsettia to bloom in time for the Christmas season, daylilies to bloom for the Easter (although Easter can be in March or April), etc.
It turns out that human beings are also influenced by the light. Light determines our sleep/wake cycle. In most animals and humans, the desire to sleep is brought on by secretion of a hormone called melatonin. Melatonin is produced in a tiny gland known as the pineal gland. In the evening the pineal gland reacts to the diminishing levels of daylight and starts to produce melatonin, which is then released into the blood and flows through the body making us drowsy. Its secretion peaks in the middle of the night during our heaviest hours of sleep. In the morning, bright light shining through the eye reaches the pineal gland which reacts by switching off the production of melatonin, thus removing the desire to sleep.
The pineal gland is linked up to the rest of the hormonal system. Consequently melatonin production also influences the functioning of other parts of the body. During darkness and sleep, melatonin modifies the secretion of hormones from organs such as the pituitary, the master gland of the hormonal system. The pituitary in turn regulates the secretion of hormones controlling growth, milk production, egg and sperm production. It also regulates the action of the thyroid gland, which is concerned with metabolism, and the adrenal glands, which control excretion of the body's waste. It is obvious then that fluctuations in light and darkness according to the seasons of the year will influence rhythms of growth, reproduction and activity in animals and indeed humans.
Statistics show that despite living and working in "closed structures", our bodies still respond to the external environment and to its seasonal variability in duration and intensity. Scientist have found that growth rates in children are affected by the seasons. For example, surveys carried out in Germany, Sweden and Scotland show that height and weight increase is more predominant in the spring and early summer. In many countries the rate of conception peaks in the summer when the hours of daylight are longest. In numerous trials the seasons have been seen to influence the timing and duration of sleep, pain threshold, alertness, eating habits, mood, the onset of menstruation in women and sexual activity.
Human beings are the product of habits and heritage. Before the advent of alarm clocks, many farmers woke up hearing the rooster crowing, announcing the arrival of morning. They milked their cows, worked in the farm and went into bed at night. There was no electricity. So, daylight announced the initiation and termination of many activities.
Modern life style differs significantly from these early days. Most of us wake up in the morning, not by hearing a rooster crow or by feeling the golden rays of sunlight slowly drifting into our rooms; we wake up by the alarm clock or by the clock radio. Many of us have tough time getting up at the first time; so we set the "snooze" button to give us a little more of precious time to sleep. The windows have heavy drapes, so most of us do not see the sunlight except when we peek outside. In the evening, many of us stay awake to watch the late night shows. (Now we have light night shows and late late night shows to keep us company till the wee hours of the night.)
The problem is that our system needs time to sleep. Studies on animals have shown that they have definite patterns they follow every day depending on the season. In autumn, most of the plants and animals get ready to go into "hibernation" for the winter period. Many birds migrate to south for the winter. During this period, they do not eat much (There is not much food to be found.) But, come spring, nature become very lively. The birds return from the south. The trees starts the new growth.
Many animals are found to time the events in their lives depending on the season, so that the functions can be accomplished at the most effective way. For example, lambs are born only in the spring when there is plentiful of food for the mother to nurse the newborn. Most of the animal species coordinate the mating time so that the birth occurs in the season when there is plenty of food available. In the tropical rainforests, birds wait till the dry season to breed. In Arctic, the breeding is timed to coincide with the melting of snow and ice.
The question is how do animals know how to predict the seasons in advance? Is it the temperature fluctuations? It cannot be, because, sometimes we have the "so called Indian Summer" in fall; but the birds do fine. It turns out that the most important factor is the day light; or more specifically the day/night cycle. Animals and plants sense the shortening of the days in the fall and perceive the arrival of winter. In spring, the lengthening of the day signifies the arrival of spring and summer. Most of the expert horticulturists know about this. They manipulate the "day light hours" (or photoperiod) to coax the poinsettia to bloom in time for the Christmas season, daylilies to bloom for the Easter (although Easter can be in March or April), etc.
It turns out that human beings are also influenced by the light. Light determines our sleep/wake cycle. In most animals and humans, the desire to sleep is brought on by secretion of a hormone called melatonin. Melatonin is produced in a tiny gland known as the pineal gland. In the evening the pineal gland reacts to the diminishing levels of daylight and starts to produce melatonin, which is then released into the blood and flows through the body making us drowsy. Its secretion peaks in the middle of the night during our heaviest hours of sleep. In the morning, bright light shining through the eye reaches the pineal gland which reacts by switching off the production of melatonin, thus removing the desire to sleep.
The pineal gland is linked up to the rest of the hormonal system. Consequently melatonin production also influences the functioning of other parts of the body. During darkness and sleep, melatonin modifies the secretion of hormones from organs such as the pituitary, the master gland of the hormonal system. The pituitary in turn regulates the secretion of hormones controlling growth, milk production, egg and sperm production. It also regulates the action of the thyroid gland, which is concerned with metabolism, and the adrenal glands, which control excretion of the body's waste. It is obvious then that fluctuations in light and darkness according to the seasons of the year will influence rhythms of growth, reproduction and activity in animals and indeed humans.
Statistics show that despite living and working in "closed structures", our bodies still respond to the external environment and to its seasonal variability in duration and intensity. Scientist have found that growth rates in children are affected by the seasons. For example, surveys carried out in Germany, Sweden and Scotland show that height and weight increase is more predominant in the spring and early summer. In many countries the rate of conception peaks in the summer when the hours of daylight are longest. In numerous trials the seasons have been seen to influence the timing and duration of sleep, pain threshold, alertness, eating habits, mood, the onset of menstruation in women and sexual activity.
Biological Clocks and The Relationship to Health
We have shown that light levels influences the life in animals and humans immensely. Scientists have performed experiments to determine how animals will react if they are deprived of light. Of particular interest was to determine, whether they can perceive the seasons in the absence of light. These studies have shown that, the animals perceived the arrival of seasons without the aid of the light. This result led them to the conclusions that the animals, and humans too, possess a biological clock in their body that can keep the approximate time in the absence of the external stimuli such as sunlight.
The interesting thing they noticed was that, this biological clock was, at best, approximate. It was not meant to keep time over a longer period of time. (This can be illustrated with the example of our spare tire in cars. Most of new cars come with a spare tire which is smaller in size. It is meant to be used, in case their tire has to puncture, to go to the nearest service station to get the main one fixed. Because the spare tire is smaller, it cannot be used to drive for extended period of time.) For example, the body clock sensed the day more than 24 hours. (The cycle was anywhere from 24 to 48 hours in the absence of light.) What we do is to use the natural daylight to "fine-tune" our body clock (or to apply a correction), so that the body clock is in synch with the external environment. The result of going for an extended period of time without having our body clocks "reset" with natural light is that we get sick with problems such as hormonal imbalances, sleep disorders, and mood disturbances.
Just as animals rely on signals from the sun to keep their body clocks exact and to synchronize their activities, so humans need sufficient daylight to synchronize their circadian and circannual rhythms.
We have shown that light levels influences the life in animals and humans immensely. Scientists have performed experiments to determine how animals will react if they are deprived of light. Of particular interest was to determine, whether they can perceive the seasons in the absence of light. These studies have shown that, the animals perceived the arrival of seasons without the aid of the light. This result led them to the conclusions that the animals, and humans too, possess a biological clock in their body that can keep the approximate time in the absence of the external stimuli such as sunlight.
The interesting thing they noticed was that, this biological clock was, at best, approximate. It was not meant to keep time over a longer period of time. (This can be illustrated with the example of our spare tire in cars. Most of new cars come with a spare tire which is smaller in size. It is meant to be used, in case their tire has to puncture, to go to the nearest service station to get the main one fixed. Because the spare tire is smaller, it cannot be used to drive for extended period of time.) For example, the body clock sensed the day more than 24 hours. (The cycle was anywhere from 24 to 48 hours in the absence of light.) What we do is to use the natural daylight to "fine-tune" our body clock (or to apply a correction), so that the body clock is in synch with the external environment. The result of going for an extended period of time without having our body clocks "reset" with natural light is that we get sick with problems such as hormonal imbalances, sleep disorders, and mood disturbances.
Just as animals rely on signals from the sun to keep their body clocks exact and to synchronize their activities, so humans need sufficient daylight to synchronize their circadian and circannual rhythms.
It has been suggested that a number of illnesses which result from hormonal imbalances - sleep, appetite, mood and reproductive disorders - could be linked to a disruption of circadian rhythms and ultimately to a lack of sufficient sunlight. SAD is an example of disturbed sleep patterns, appetite and weight disorders and depression, all of which manifest in a yearly and daily cycle: the symptoms peak at the height of winter and are at their worst in the evening. Giving SAD patients artificial daylight (light therapy) has proved successful in correcting these disorders, which suggests that SAD is directly associated with a lack of sufficient light.
There are other diseases that are influenced by the circadian rhythm disturbances. Classical depression has a daily rhythm. It worsens in the morning and improves in the evening. The result of this swing is the appearance of mood swings, along with insomnia or disturbed sleep patterns. Today, classical depression is often treated with drugs which exert an influence on circadian rhythms. Research is being carried out to determine the effectiveness of treating it with light therapy. Menstrual disturbances in women, such as irregular menstrual cycles or premenstrual syndrome are further examples of disturbances in the body's biological clocks. Again research is looking at the possibility of treatment with light therapy
There are other diseases that are influenced by the circadian rhythm disturbances. Classical depression has a daily rhythm. It worsens in the morning and improves in the evening. The result of this swing is the appearance of mood swings, along with insomnia or disturbed sleep patterns. Today, classical depression is often treated with drugs which exert an influence on circadian rhythms. Research is being carried out to determine the effectiveness of treating it with light therapy. Menstrual disturbances in women, such as irregular menstrual cycles or premenstrual syndrome are further examples of disturbances in the body's biological clocks. Again research is looking at the possibility of treatment with light therapy
Brain, Hormones, Biological Cycles and Clocks
In order to understand the mechanism of Seasonal Affective disorder and the effect of light on our mind, it is necessary to get an understanding of how our body and brain work. We will introduce some important terms in this section to augment our understanding.
Our brain manages a number of complicated body processes, breathing, digestion, circulation, growth, reproduction, and repair. These brain utilizes two separated systems to control these processes, the nervous system and the endocrine system.
The nervous system is the fastest out of the two. Two send a message fast, the brain uses the nervous system. The messages are generally brief (such as a few thousandths of a second). The nervous system employs electrical impulses that travel through nerve cells as fast as 650 feet (200 meters) per second.
The endocrine system sends most messages slowly. It uses hormones to produce more long lasting effects. Hormonal messages travel through the blood stream. It may take several hours or days to reach the destination or to effect a change. Endocrine system is a collection of ductless glands throughout the body that secrete hormones directly into the blood stream. These glands include the pituitary, thyroid, thymus, adrenals, pancreas, ovaries or testes, and many others. The function of these glands are to control the internal environment of the entire body.
The difference between nervous system and endocrine system can be illustrated as follows. Let us say we need to send an article from the United States to Asia. The fastest way to send it is by air mail or express mail. It will take a few days. Since it is expensive, we will only utilize the medium for small things such as a letter. The other way to send is by surface mail (by ship). This takes a few months to get there; but is relatively cheap compared to air mail. Normally, big, bulky items are transported by this means. In this analogy, air mail is like the nervous system and the surface mail is like the endocrine system. Depending on the amount of material to send and the urgency of the message, the brain chooses either one of these systems.
Hypothalamus
Hypothalamus is known as the brain behind the endocrine system. The main vehicle used by hypothalamus is the pituitary (a pea sized gland that sits under the hypothalamus) to control other glands. The hypothalamus weighs a fraction of an ounce. It is about the size of the tip of our thumb.
For example, when hypothalamus determines that the level of thyroid hormone in the blood need to be increased, it releases a hormone to the pituitary gland instructing it to convey the message to the thyroid gland. The pituitary immediately sends a thyroid stimulating hormone to the thyroid instructing it to release more thyroid. When thyroid receives this message, it will start releasing the thyroid hormone called thyroxin. When this happens, the metabolic rates are speeded up. In the same fashion, hypothalamus controls the other endocrine systems, thus controlling such things as the sugar level in the blood, the body temperature, etc.
Pineal Gland
Pineal Gland is a tiny pine-cone shaped (the name is from the resemblance of the shape of the organ to the pine cone) organ located at the back of the brain, just above the brain stem.
Many scientists believe that pineal gland is the "aging clock" for the body. It appears to act as the body's timekeeper by keeping the body in sync with the most constant environmental cue we have: the light-dark cycle.
It is the pineal's job to announce to the rest of the body that it is dawn or dusk, time for the body to be awake and alert, or time to prepare for bed and a rejuvenating sleep. This crucial signal sets complex processes into motion, a cycle that is designed to remain relatively regular and balanced. The circadian rhythm (see below for an explanation) lies at the heart of the state of internal balance and harmony we know of as health. When it becomes disrupted over a long period of time, there may be serious physical and psychological consequences.
At the same time, the pineal gland also appears to act as the body's pacemaker, a kind of "activities director" for the human life cycle. Scientists believe that the pineal gland, through its major product, melatonin, triggers the start of puberty and regulates reproductive life. When the pineal gland stops giving out its melatonin-directed signals, we grow old because our bodies are no longer able to operate with efficiency or with internal synchronicity.
Melatonin
Melatonin is produced by the pineal gland. Scientists believe that the pineal gland and melatonin are the body's primary timekeepers-its clock and calendar-imparting information about the time of day, season of the year, and phase of life to the brain and throughout the body. Melatonin is believed to influence the internal processes so that all of the body's systems work together, in coordination. Should this internal structure become disorganized in any way, the body becomes more susceptible to disease.
Melatonin is produced almost exclusively at night or in a light-free environment. (In fact, it is nicknamed "the chemical expression of darkness" by scientists because of its nocturnal habits.) Blood levels of melatonin are up to ten times greater at night than during the day. This high concentration of nocturnal melatonin led scientists to conclude that the production of this hormone signals to the rest of the body that it is time to sleep. Indeed, melatonin supplements have been used for decades to treat sleep-related problems, such as insomnia, sleep apnea, and jet lag.
In the morning, when we perceive that it is light, melatonin secretion ceases, which stimulates the production of other hormones and hence other body activities to begin. This orderly daily rhythm is of prime importance to our physical condition, intellectual capabilities, and emotional health.
Animals change their behaviors such as reproduction, hibernation, and migration based on the season. It is believed that animals perceive the change of seasons by the patterns of light and dark. The mechanism used to implement this behavior is by the secretion of melatonin. When daylight hours grow shorter during the autumn months, melatonin production in animals automatically increases, helping to make the almost constant sleep of hibernation possible. When daylight hours increase during the spring, the pineal gland secretes less melatonin, triggering a new pattern of physical activity.
The ways in which these seasonal patterns affect human behavior is under intense investigation. Some researchers believe that seasonal melatonin levels may help to explain Seasonal Affective Disorder.
Chronobiology is a new science that is concerned with identifying our cycles and internal clocks and seeing how they interact. Such natural rhythms as temperature fluctuations, weather systems, patterns of light and dark are studied to explore how it affects the life cycle of men and women.
Melatonin and Serotonin
Melatonin affects the production and subsequent action of several other hormone in the body. It works in sync with serotonin, a powerful neurotransmitter from which it is derived. Serotonin is involved in several central physiological processes, including pain perception, temperature and blood-pressure regulation, and several neuropsychological functions such as appetite, memory, and mood. Like melatonin, serotonin levels influence a myriad of endocrine activities, including those performed by the hypothalamus and pituitary gland.
Generally speaking, melatonin and serotonin are not active in the body at the same time. As mentioned earlier, melatonin is active at night, serotonin is active in the daytime. Although both tend to moderate endocrine functions, serotonin may also have a negative effect on the cardiovascular system if its levels are too high in the bloodstream. It has been known to cause blood clotting and narrowing of the blood vessels, among other problems. And, unlike melatonin, serotonin levels in the body do not decrease as we age, but instead increase in relation to other hormones and neurotransmitters. Scientists who specialize in the study of elderly and the aging process believe that this age-related imbalance between serotonin and melatonin may play as important a role in the aging process as the lack of melatonin itself, particularly in relation to heart disease. Without melatonin to act as a free-radical scavenger during the night, more damage may occur to blood vessels, thus stimulating the release of more serotonin.
Research has also shown that in very depressed people, there is a shortage of serotonin, along with dopamine and norepinephrine, three of the neurotransmitters used by the brain. So, the serotonin and melatonin link along with their dependence on the body clock may explain the depression experienced by the people suffering from SAD.
In order to understand the mechanism of Seasonal Affective disorder and the effect of light on our mind, it is necessary to get an understanding of how our body and brain work. We will introduce some important terms in this section to augment our understanding.
Our brain manages a number of complicated body processes, breathing, digestion, circulation, growth, reproduction, and repair. These brain utilizes two separated systems to control these processes, the nervous system and the endocrine system.
The nervous system is the fastest out of the two. Two send a message fast, the brain uses the nervous system. The messages are generally brief (such as a few thousandths of a second). The nervous system employs electrical impulses that travel through nerve cells as fast as 650 feet (200 meters) per second.
The endocrine system sends most messages slowly. It uses hormones to produce more long lasting effects. Hormonal messages travel through the blood stream. It may take several hours or days to reach the destination or to effect a change. Endocrine system is a collection of ductless glands throughout the body that secrete hormones directly into the blood stream. These glands include the pituitary, thyroid, thymus, adrenals, pancreas, ovaries or testes, and many others. The function of these glands are to control the internal environment of the entire body.
The difference between nervous system and endocrine system can be illustrated as follows. Let us say we need to send an article from the United States to Asia. The fastest way to send it is by air mail or express mail. It will take a few days. Since it is expensive, we will only utilize the medium for small things such as a letter. The other way to send is by surface mail (by ship). This takes a few months to get there; but is relatively cheap compared to air mail. Normally, big, bulky items are transported by this means. In this analogy, air mail is like the nervous system and the surface mail is like the endocrine system. Depending on the amount of material to send and the urgency of the message, the brain chooses either one of these systems.
Hypothalamus
Hypothalamus is known as the brain behind the endocrine system. The main vehicle used by hypothalamus is the pituitary (a pea sized gland that sits under the hypothalamus) to control other glands. The hypothalamus weighs a fraction of an ounce. It is about the size of the tip of our thumb.
For example, when hypothalamus determines that the level of thyroid hormone in the blood need to be increased, it releases a hormone to the pituitary gland instructing it to convey the message to the thyroid gland. The pituitary immediately sends a thyroid stimulating hormone to the thyroid instructing it to release more thyroid. When thyroid receives this message, it will start releasing the thyroid hormone called thyroxin. When this happens, the metabolic rates are speeded up. In the same fashion, hypothalamus controls the other endocrine systems, thus controlling such things as the sugar level in the blood, the body temperature, etc.
Pineal Gland
Pineal Gland is a tiny pine-cone shaped (the name is from the resemblance of the shape of the organ to the pine cone) organ located at the back of the brain, just above the brain stem.
Many scientists believe that pineal gland is the "aging clock" for the body. It appears to act as the body's timekeeper by keeping the body in sync with the most constant environmental cue we have: the light-dark cycle.
It is the pineal's job to announce to the rest of the body that it is dawn or dusk, time for the body to be awake and alert, or time to prepare for bed and a rejuvenating sleep. This crucial signal sets complex processes into motion, a cycle that is designed to remain relatively regular and balanced. The circadian rhythm (see below for an explanation) lies at the heart of the state of internal balance and harmony we know of as health. When it becomes disrupted over a long period of time, there may be serious physical and psychological consequences.
At the same time, the pineal gland also appears to act as the body's pacemaker, a kind of "activities director" for the human life cycle. Scientists believe that the pineal gland, through its major product, melatonin, triggers the start of puberty and regulates reproductive life. When the pineal gland stops giving out its melatonin-directed signals, we grow old because our bodies are no longer able to operate with efficiency or with internal synchronicity.
Melatonin
Melatonin is produced by the pineal gland. Scientists believe that the pineal gland and melatonin are the body's primary timekeepers-its clock and calendar-imparting information about the time of day, season of the year, and phase of life to the brain and throughout the body. Melatonin is believed to influence the internal processes so that all of the body's systems work together, in coordination. Should this internal structure become disorganized in any way, the body becomes more susceptible to disease.
Melatonin is produced almost exclusively at night or in a light-free environment. (In fact, it is nicknamed "the chemical expression of darkness" by scientists because of its nocturnal habits.) Blood levels of melatonin are up to ten times greater at night than during the day. This high concentration of nocturnal melatonin led scientists to conclude that the production of this hormone signals to the rest of the body that it is time to sleep. Indeed, melatonin supplements have been used for decades to treat sleep-related problems, such as insomnia, sleep apnea, and jet lag.
In the morning, when we perceive that it is light, melatonin secretion ceases, which stimulates the production of other hormones and hence other body activities to begin. This orderly daily rhythm is of prime importance to our physical condition, intellectual capabilities, and emotional health.
Animals change their behaviors such as reproduction, hibernation, and migration based on the season. It is believed that animals perceive the change of seasons by the patterns of light and dark. The mechanism used to implement this behavior is by the secretion of melatonin. When daylight hours grow shorter during the autumn months, melatonin production in animals automatically increases, helping to make the almost constant sleep of hibernation possible. When daylight hours increase during the spring, the pineal gland secretes less melatonin, triggering a new pattern of physical activity.
The ways in which these seasonal patterns affect human behavior is under intense investigation. Some researchers believe that seasonal melatonin levels may help to explain Seasonal Affective Disorder.
Chronobiology is a new science that is concerned with identifying our cycles and internal clocks and seeing how they interact. Such natural rhythms as temperature fluctuations, weather systems, patterns of light and dark are studied to explore how it affects the life cycle of men and women.
Melatonin and Serotonin
Melatonin affects the production and subsequent action of several other hormone in the body. It works in sync with serotonin, a powerful neurotransmitter from which it is derived. Serotonin is involved in several central physiological processes, including pain perception, temperature and blood-pressure regulation, and several neuropsychological functions such as appetite, memory, and mood. Like melatonin, serotonin levels influence a myriad of endocrine activities, including those performed by the hypothalamus and pituitary gland.
Generally speaking, melatonin and serotonin are not active in the body at the same time. As mentioned earlier, melatonin is active at night, serotonin is active in the daytime. Although both tend to moderate endocrine functions, serotonin may also have a negative effect on the cardiovascular system if its levels are too high in the bloodstream. It has been known to cause blood clotting and narrowing of the blood vessels, among other problems. And, unlike melatonin, serotonin levels in the body do not decrease as we age, but instead increase in relation to other hormones and neurotransmitters. Scientists who specialize in the study of elderly and the aging process believe that this age-related imbalance between serotonin and melatonin may play as important a role in the aging process as the lack of melatonin itself, particularly in relation to heart disease. Without melatonin to act as a free-radical scavenger during the night, more damage may occur to blood vessels, thus stimulating the release of more serotonin.
Research has also shown that in very depressed people, there is a shortage of serotonin, along with dopamine and norepinephrine, three of the neurotransmitters used by the brain. So, the serotonin and melatonin link along with their dependence on the body clock may explain the depression experienced by the people suffering from SAD.
Professor Mester of Budapest University conducted experiments to determine the function of light in the cells of animals and humans. He found that the monochromatic light promotes the DNA to use the lipoprotein in the area enabling the the cell to function better as well as to produce collagen and elastin.
In a study reported in the American Geriatrics Society, researchers wanted to find out "the effects of low-power light therapy on pain and disability in elderly patients with degenerative osteoarthritis of the knee." They have divided the patients into three groups. One group was treated with red light, one was treated with infrared light and the third group got no light therapy. Prior to the light therapy, the pain and disability was statistically similar among the three control groups. They found that pain reduction in the red and infrared groups after the treatment was more than 50%. Significant functional improvement was observed in the red and infrared-treated groups, but not in the placebo group. The experiment showed that low-power light therapy is effective in relieving pain and disability in degenerative osteoarthritis of the knee.
Research conducted in Soviet Union and biological research done in the United States suggest that all living things may conduct light. Light has a great impact on synchronizing our circadian rhythms.
In fact, researchers have determined several benefits from regular, moderate exposure to sunlight-or to sun-like artificial lights. Such exposure can help relieve winter blues and treat other forms of depression; minimize jet lag; shorten abnormally long menstrual cycles and treat psoriasis, eating disorders and some forms of insomnia. It can possibly even help relieve some symptoms of lupus-a serious disease involving the immune system.
Circadian Rhythm
From the Latin circa (about) dies (a day), the circadian rhythm is the twenty-four-hour cycle of light/dark, wakefulness/sleep to which most human physiologic processes are set. At regular intervals each day, the body tends to become hungry, tired, active, listless, energized. Body temperature, heart-beat, blood pressure, hormone levels, and urine flow rise and fall in this relatively predictable, rhythmic pattern - a pattern initiated and governed by exposure to sunlight and darkness.
Experiments where humans were placed in isolation chambers, cut off from all potential environmental cues, have shown that, in the absence of natural daylight, rhythms are still maintained. But in the absence of the day light, the rhythms tend to deviate from 24 hours. For instance, the rhythms was found to expand to 24-30 hours, thus disrupting the biological processes over a long period of time.
The fact that animals and humans can continue to function according to daily and annual rhythms in the absence of external environmental stimuli means that animals and humans possess some kind of biological clock, which act as a backup mechanism in case it cannot get the proper stimuli from the natural events such as sunshine.
This behavior can be illustrated by our clocks. Let us say, our clock is running slow. Over a period of time, the clock may lag the actual time because of this defect. Usually, we will reset the clock when it gets far out of sync by other external stimuli like a radio or phone time. Now, if we do not have access to this external synchronizing signal, the clock can get far out of line with the reality. Our body clocks functions the same way. The biological clock can keep the time; but in the absence of correction from the day/light cycle provided by the sun, the biological clock tend go out of sync affecting our physical and mental health. A similar thing happens when we travel across time zones; we tend to experience what is known as "jet lag".
However, in the absence of natural light our body clocks may lose or gain a little time. This in turn could lead to the desynchronization of different rhythms. For example, in the absence of sufficient environmental light the sleep-wake and associated rest-activity rhythms may lengthen to a cycle of between 30 and 48 hours, while the temperature rhythm may remain at a period of, say, 25 hours. Such desynchronization of the body's intricate rhythms is suspected to trigger problems: hormonal imbalances, sleep disorders and mood disturbances.
Circannual Rhythm
Circannual rhythm is the annual or yearly cycle used by all living things.
Circaseptan Rhythm
Circaseptan rhythm is a seven-day cycle in which the biological processes of life, including disease symptoms and development, resolve. Many physicians believe that transplant patients tend to have more rejection episodes seven, fourteen, twenty-one, and twenty-eight days after surgery. They further believe that medications administered to the patients at particular times may be more effective than at other times. These are all related to the circaseptan rhythm.
How does the brain know when it is light or dark?
Deep within the brain, inside the hypothalamus, lie two clusters of cells (i.e., neurons) called the suprachiasmatic nuclei (SCN). Each of these SCN is composed of more than 8,000 neurons. The SCN act as the body's circadian pacemaker. In mammals, the SCN appear to get their information from photoreceptors in the retina, which transmit signals about light and dark through the optic nerves to the hypothalamus. Once these messages enter the SCN, a series of physiological reactions takes place.
What happens after the light/dark signal reaches the SCN?
We are not sure. The pathway from the retina through the optic nerves to the SCN extends further to reach the pineal gland, which lies adjacent to the hypothalamus above the brain stem. Stimulated by the message it receives from the SCN, the pineal gland either secretes its main hormone, melatonin, or inhibits melatonin's release, which may result in the production of serotonin as was explained before.
From the Latin circa (about) dies (a day), the circadian rhythm is the twenty-four-hour cycle of light/dark, wakefulness/sleep to which most human physiologic processes are set. At regular intervals each day, the body tends to become hungry, tired, active, listless, energized. Body temperature, heart-beat, blood pressure, hormone levels, and urine flow rise and fall in this relatively predictable, rhythmic pattern - a pattern initiated and governed by exposure to sunlight and darkness.
Experiments where humans were placed in isolation chambers, cut off from all potential environmental cues, have shown that, in the absence of natural daylight, rhythms are still maintained. But in the absence of the day light, the rhythms tend to deviate from 24 hours. For instance, the rhythms was found to expand to 24-30 hours, thus disrupting the biological processes over a long period of time.
The fact that animals and humans can continue to function according to daily and annual rhythms in the absence of external environmental stimuli means that animals and humans possess some kind of biological clock, which act as a backup mechanism in case it cannot get the proper stimuli from the natural events such as sunshine.
This behavior can be illustrated by our clocks. Let us say, our clock is running slow. Over a period of time, the clock may lag the actual time because of this defect. Usually, we will reset the clock when it gets far out of sync by other external stimuli like a radio or phone time. Now, if we do not have access to this external synchronizing signal, the clock can get far out of line with the reality. Our body clocks functions the same way. The biological clock can keep the time; but in the absence of correction from the day/light cycle provided by the sun, the biological clock tend go out of sync affecting our physical and mental health. A similar thing happens when we travel across time zones; we tend to experience what is known as "jet lag".
However, in the absence of natural light our body clocks may lose or gain a little time. This in turn could lead to the desynchronization of different rhythms. For example, in the absence of sufficient environmental light the sleep-wake and associated rest-activity rhythms may lengthen to a cycle of between 30 and 48 hours, while the temperature rhythm may remain at a period of, say, 25 hours. Such desynchronization of the body's intricate rhythms is suspected to trigger problems: hormonal imbalances, sleep disorders and mood disturbances.
Circannual Rhythm
Circannual rhythm is the annual or yearly cycle used by all living things.
Circaseptan Rhythm
Circaseptan rhythm is a seven-day cycle in which the biological processes of life, including disease symptoms and development, resolve. Many physicians believe that transplant patients tend to have more rejection episodes seven, fourteen, twenty-one, and twenty-eight days after surgery. They further believe that medications administered to the patients at particular times may be more effective than at other times. These are all related to the circaseptan rhythm.
How does the brain know when it is light or dark?
Deep within the brain, inside the hypothalamus, lie two clusters of cells (i.e., neurons) called the suprachiasmatic nuclei (SCN). Each of these SCN is composed of more than 8,000 neurons. The SCN act as the body's circadian pacemaker. In mammals, the SCN appear to get their information from photoreceptors in the retina, which transmit signals about light and dark through the optic nerves to the hypothalamus. Once these messages enter the SCN, a series of physiological reactions takes place.
What happens after the light/dark signal reaches the SCN?
We are not sure. The pathway from the retina through the optic nerves to the SCN extends further to reach the pineal gland, which lies adjacent to the hypothalamus above the brain stem. Stimulated by the message it receives from the SCN, the pineal gland either secretes its main hormone, melatonin, or inhibits melatonin's release, which may result in the production of serotonin as was explained before.
Light Therapy for Seasonal Affective Disorders
One of the most important applications of light therapy is in the treatment of Seasonal Affective Disorders (SAD). There is a large body of scientific evidence that points to the efficacy of light therapy for the treatment of SAD. What is not quite understood, yet, is how light treatment works.
We have shown that our daily rhythms are affected by the availability of the natural sun light. Many of us work in artificially lit buildings and does not get enough light. Most artificial lighting cannot replace the natural light. The reason for this is that the type of indoor lighting we use is not of sufficient intensity to affect the hormonal mechanisms which control our bodily rhythms. Intensity of light is measured in a unit called lux. One lumen means the light received by the receptor at an intensity of one lumen per square meter. Thus the intensity of light at any point is determined not only by the strength of the illumination source but also by how far it is from the source. The electric light used in most homes and workplaces rarely exceeds 500 lux. A sunny afternoon could be as much as 100,000 lux, and even the cloudiest day is rarely below 10,000 lux. Researchers have discovered that light of at least 2,500 lux is necessary to suppress melatonin production in humans. Most of the bright light therapy uses 5000 lux light (10,000 lux preferred.) The artificial light we use indoors is not of sufficient intensity to suppress melatonin and to correct the circadian rhythm. Night-shift workers, and people who live in Arctic climates, are usually exposed to light levels of only 50 lux. Light specialists believe this "mal-illumination" may be at the heart of many common disorders, including fatigue, depression, skin damage, suppressed immune function, and, of course, sleep problems.
Light therapy for Seasonal Affective Disorders and circadian-rhythm disorders involves sending visible light through the eyes so that it reaches, and triggers, the pineal gland.
There are several different forms of light therapy in use today; the oldest is sunlight itself. The sun is the ultimate source of full-spectrum light, which means it contains all possible wavelengths of light, from infrared to ultraviolet. Generally speaking light therapy involves the use of equipment that sheds either full spectrum or bright white light.
In most cases, the purpose of light therapy is to increase the amount of light to which we would otherwise be exposed. Bright light therapy consists of looking at special broad spectrum bright lights from one-half to three hours a day, generally in the early morning hours. One should not stare directly into the lights because of possible eye damage.
A substantial amount of light is needed, which means the distance from the lights to your eyes needs to be monitored---close enough to give you the best amount of light, but distant enough so you don't hurt your eyes.
By the mid- 1980s, bright-light therapy (phototherapy) had become the treatment of choice for SAD. But many people found it difficult to allocate the four hours everyday for the light therapy. Additional studies were conducted by the researchers to determine an optimum light therapy. It was found that similar benefits can be obtained from a morning only therapy, effectively slashing the time by half. Later, by increasing the brightness or the intensity of the lights used, the therapy time was cut down further.
A few years later, it was cut further by brightening the lights. For example, with 10,000-lux light, it only required 30 minutes of exposure per day to get effective cure from SAD.
SAD symptoms typically begin to lift about a week after the start of phototherapy. But they return shortly after discontinuing the treatment. As a result, authorities urge people with SAD to sit under bright light daily from October through April.
One of the most important applications of light therapy is in the treatment of Seasonal Affective Disorders (SAD). There is a large body of scientific evidence that points to the efficacy of light therapy for the treatment of SAD. What is not quite understood, yet, is how light treatment works.
We have shown that our daily rhythms are affected by the availability of the natural sun light. Many of us work in artificially lit buildings and does not get enough light. Most artificial lighting cannot replace the natural light. The reason for this is that the type of indoor lighting we use is not of sufficient intensity to affect the hormonal mechanisms which control our bodily rhythms. Intensity of light is measured in a unit called lux. One lumen means the light received by the receptor at an intensity of one lumen per square meter. Thus the intensity of light at any point is determined not only by the strength of the illumination source but also by how far it is from the source. The electric light used in most homes and workplaces rarely exceeds 500 lux. A sunny afternoon could be as much as 100,000 lux, and even the cloudiest day is rarely below 10,000 lux. Researchers have discovered that light of at least 2,500 lux is necessary to suppress melatonin production in humans. Most of the bright light therapy uses 5000 lux light (10,000 lux preferred.) The artificial light we use indoors is not of sufficient intensity to suppress melatonin and to correct the circadian rhythm. Night-shift workers, and people who live in Arctic climates, are usually exposed to light levels of only 50 lux. Light specialists believe this "mal-illumination" may be at the heart of many common disorders, including fatigue, depression, skin damage, suppressed immune function, and, of course, sleep problems.
Light therapy for Seasonal Affective Disorders and circadian-rhythm disorders involves sending visible light through the eyes so that it reaches, and triggers, the pineal gland.
There are several different forms of light therapy in use today; the oldest is sunlight itself. The sun is the ultimate source of full-spectrum light, which means it contains all possible wavelengths of light, from infrared to ultraviolet. Generally speaking light therapy involves the use of equipment that sheds either full spectrum or bright white light.
In most cases, the purpose of light therapy is to increase the amount of light to which we would otherwise be exposed. Bright light therapy consists of looking at special broad spectrum bright lights from one-half to three hours a day, generally in the early morning hours. One should not stare directly into the lights because of possible eye damage.
A substantial amount of light is needed, which means the distance from the lights to your eyes needs to be monitored---close enough to give you the best amount of light, but distant enough so you don't hurt your eyes.
By the mid- 1980s, bright-light therapy (phototherapy) had become the treatment of choice for SAD. But many people found it difficult to allocate the four hours everyday for the light therapy. Additional studies were conducted by the researchers to determine an optimum light therapy. It was found that similar benefits can be obtained from a morning only therapy, effectively slashing the time by half. Later, by increasing the brightness or the intensity of the lights used, the therapy time was cut down further.
A few years later, it was cut further by brightening the lights. For example, with 10,000-lux light, it only required 30 minutes of exposure per day to get effective cure from SAD.
SAD symptoms typically begin to lift about a week after the start of phototherapy. But they return shortly after discontinuing the treatment. As a result, authorities urge people with SAD to sit under bright light daily from October through April.
