Seasonal Affective Disorder (SAD), also known as winter blues or winter depression is a type of depression that occurs during the winter months. It comes with the shortening of the days in late autumn and may last until spring. (It also occurs in the summer, summer blues/depression, although in this article I speak of winter.) It used to be considered a mood disorder, but it is now classified as a specifier called With seasonal depression for recurrent major depressive disorder that occurs at a specific time of year and fully remits otherwise.
Some signs and symptoms of SAD include difficulty in getting out of bed in the morning, nausea, and tendency to oversleep and over-eat, especially carbohydrates which can lead to weight gain. Other symptoms include lack of energy, difficulty concentrating, and social withdrawal.
It has been argued that SAD is an evolved adaptation in humans that is a hibernation response in our ancestors. Because food was scarce in winter months we adapted to reduce food intake.
Research shows a few forms of management which include light therapy, some anti-depressants, and increased dose of Vitamin D. Research further shows that increasing physical activity during the winter months significantly reduces symptoms of SAD. In other words, don't hibernate, prepare for winter and face it head on with gusto, knowing that in a few months spring will inevitably break.