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, 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 th ....

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.... 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 effects 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 ....