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Seasonal Affective Disorder, or SAD, is officially recognised by Doctors and Psychiatrists as a medical condition that is thought to affect 2 million people in Great Britain. In the beginning man only worked and lived outdoors in full natural daylight. At the turn of the 19th century 75% of the population worked outdoors. Now less than 10% of the population work in natural outdoor light. This change has resulted in a dramatic increase in light deficiency symptoms. Symptoms include: