Seasonal Affective Disorder (SAD), also known as winter depression or winter blues, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or, less frequently, in the summer, spring or autumn, repeatedly, year after year. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), SAD is not a unique mood disorder, but is "a specifier of major depression".
Symptoms of SAD may consist of: difficulty waking up in the morning [check], tendency to oversleep as well as to overeat [check], and especially a craving for carbohydrates [check], which leads to weight gain [check]. Other symptoms include a lack of energy [check], difficulty concentrating on completing tasks [check], and withdrawal from friends [check], family [check], and social activities [check]. All of this leads to the depression [check], pessimism [check], and lack of pleasure [check] which characterize a person suffering from this disorder.