Seasonal affective disorder (also called SAD) is a type of depression that follows the seasons. The most common type of SAD is called winter depression. It usually begins in late fall or early winter and normal mood returns in summer. A less common type of SAD, known as summer depression, usually begins in the late spring or early summer. SAD may be related to changes in the amount of daylight you get. (Just so you all know - John wrote this, not Becky)