Seasonal affective disorder (SAD) is a mood disorder subset in which people who typically have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year. It is commonly, but not always, associated with the reductions or increases in total daily sunlight hours that occur during the summer or winter. Common symptoms include sleeping too much, having little to no energy, and overeating. The condition in the summer can include heightened anxiety. In the DSM-IV and DSM-5, its status as a standalone condition was changed: It is no longer classified as a unique mood disorder, but is now a specifier (called "with seasonal pattern") for recurrent major depressive disorder that occurs at a specific time of the year and fully remits otherwise. Although experts were initially skeptical, this condition is now recognized as a common disorder. The validity of SAD was called into question, however, by a 2016 analysis by the Centers for Disease Control in which no links were detected between depression and seasonality or sunlight exposure. In the United States, the percentage of the population affected by SAD ranges from 1.4% of the population in Florida to 9.9% in Alaska. SAD was formally described and named in 1984, by Norman E. Rosenthal and colleagues at the National Institute of Mental Health. উৎস: Wikipedia (en)