High Quality Content by WIKIPEDIA articles! Seasonal affective disorder (SAD), also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn 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."