Years ago, medical researchers identified a disorder that appropriately named psychological People who understand SAD become Seasonal Affective Disorder, or SAD. Doctors now the causes very depressed during the winter mont people, particularly in of this condition, which affects millions of the hours of daylight are areas of the far north where winter nights are long and few. SAD results from a decrease in the amount of sufferers receive Doctors know that decreased sunlight increases the production of melatonin a sleep-related hormone that is produced at increased levels in the dark Therefore, when the days are shorter and darker, the production of this hormone increases. Shorter, darker days also decrease production of seratonin, a chemical that helps transmit nerve impulses. Lack of seratonin is known to be a cause of depression("Seasonal" HH, par 1). Depression may result from the resulting imbalance of these two substances in the body. Also, doctors believe that a decrease in the amount of sunlight the body receives may cause a disturbance in the body's natural clock("Seasonal" NMHA, par. 2). Doctors believe that the combination of chemical imbalance and biological clock disturbance results in symptoms such as lethargy, oversleeping, weight gain anxiety, and irritability--all signs of depression 3 Since absence of light seems to be the cause of this disorder, a daily dose of light appears to be the cure. Doctors advise patients to sit in front b that simulatesl natural light for a few hours every day,increases. Shorter, darker days also decrease production of seratonin, a chemical that helps transmit nerve impulses. Lack of seratonin is known to be a cause of depression("Seasonal" HH, par 1). Depression may result from the resulting imbalance of these two substances in the body. Also, doctors believe that a decrease in the amount of sunlight the body receives may cause a disturbance in the body's natural clock("Seasonal" NMHA, par. 2). Doctors believe that the combination of chemical imbalance and biological clock disturbance results in symptoms such as lethargy, oversleeping, weight gain anxiety, and irritability--all signs of depression 3 Since absence of light seems to be the cause of this disorder, a daily dose of light appears to be the cure. Doctors advise patients to sit in front b that simula