Seasonal Affective Disorder, or SAD, is a common problem of people living in northern United States. People who are affected by this disorder commonly suffer from depression, lethargy, inability to concentrate, overeating and weight gain. People from the north tend to suffer more from this disorder because of the shortened days. It appears, that due to the deficiency of sunlight some people suffer from these symptoms. The shortened days have a hormonal effect on the body that causes these symptoms, and the use of artificial sunlight is the best way to relieve the disorder. It was not until recently that SAD was discovered. It was discovered by Peter Mueller, who was reviewing a case of a 29-year-old woman. He had noticed a pattern, the woman’s depression came in the winters and left in the spring.
Over the course of years the woman moved from city to city. Mueller noticed, that the farther north she moved the early the 
depression. Mueller had begun to speculate that the lack of sunlight had contributed to the women’s depression. In order to confirm this he exposed the patient to artificial sunlight. He found that over a period of time the patient had recovered from the depression. Today light therapy is the most commonly used method in treating SAD. The two hormones that are affected by the sunlight, and are thought to be the cause of SAD, are melatonin and serotonin. Both of these chemicals “are influenced by photoperiodism, the earth’s daily dark-light cycle” (Wurtman 1989). Melatonin is the chemical that affects mood and energy levels. In the human body melatonin is at its highest at night and is lowest in the day. There has been a study done to see if sunlight has a direct effect on suppressing melatonin. It is known that melatonin levels in urine are five times higher at night than they are in the day. It was not until a 1980 study that it was known that melatonin levels could be directly suppressed with light. In an experiment, subjects were woken up at two in the morning and exposed to a half an hour of artificial sunlight. The findings were that melatonin levels were greatly decreased.
The decline in melatonin usually happens in the early morning, but in a SAD patient this does not occur until about two hours later. In order to suppress the levels the patient needs to be exposed to sunlight. It is found, that when the patient is exposed to the light there is a significant decrease in depression and the craving for carbohydrates. It is not known if SAD is directly caused by melatonin. We are still not sure what the direct cause for the depression of SAD is. We do know why people who suffer from SAD crave carbohydrates. Serotonin is the chemical that regulates a person’s appetite for carbohydrate rich foods. A patient who suffers from SAD, and is given an artificial shot of serotonin called d-fenfluramine “leads to a decrease in stress-induced eating” (Scientific American 1986). In each person blood stream we have a hormone known as trypton that is a derivative of serotonin. When it enters the central nervous system and reaches a group of cells called raphe nucli it is converted into serotonin. The amount of trypton in the blood is increased when carbohydrates are consumed. This may explain why many people who suffer from SAD have an increase their intake of carbohydrates. In testing results it patients who suffer from SAD when given “an 800-calorie, high-carbohydrate meal (six cookies), they reported feeling vigorous and energized” (Health 1989). A large consumption of carbohydrates is one of the symptoms of SAD. In a number of cases, it has been noted that in the fall a person suffering from SAD will increase their intake of carbohydrates and decrease in the summer. It is also found, that those who crave carbohydrates tend to consume most of them in the late afternoon or early evening. A carbohydrate craver is found to eat 1,940 calories at a mealtime. The average for an adult female is 1,500 to 2,00 calories, an adult male from 2,200 to 2,700 calories. It is in the early evening that the craver consumes “an additional 800 or more calories person per day” (Wurtman 1989). The increase of carbohydrates leads to an increase in the levels of serotonin that relieves the symptoms of SAD. The evidence all seems to push towards lack of daylight as the reason for SAD. Little 
research, although, has been done on the effects of temperature and barometric pressure on mental health.
These factors change during different times of the year. In his lifetime Abraham Lincoln suffered from two sever bouts with depression. Both of them came “during the two largest barometric pressure changes recorded at that time” (Davis 1994). There is the possibility that the symptoms of SAD are caused by other seasonable changes besides daylight. Evidently, the best treatment for those who suffer from SAD is light therapy. Although, we still are not for sure what the cause of SAD is we do know that light therapy suppresses the symptoms. The human body needs to be exposed to the daylight, and our everyday lives may hinder our exposure. For example, most people work inside in either an office or some type of building. This significantly reduces our exposure to daylight. It was found in San Diego that the male spent in a day an average of seventy-five minutes in the sun, and the female spent an average of twenty. The human body needs more exposure to the light to regulate the secretion of serotonin and melatonin. There is still much testing that needs to be done on SAD. We still are not sure of the cause but we do have a solution. The best way to help suppress SAD is by artificial sun lamps, but these lamps are expensive. Many of the bulbs that are used cost over one-hundred dollars. Carbohydrates are an alternate way to suppress the symptoms, but the side effect is weight gain. It has been proven in studies, which those who crave carbohydrates also put on significant weight which is lost in the spring. Exposure to daylight will suppress the symptoms without any side effects. The best method to regulate the hormonal balance is by regular exposure to daylight.
