What is seasonal affective disorder (SAD)?
Seasonal affective disorder (SAD) is a form of depression that occurs at the same time each year, usually in winter. Otherwise known as seasonal depression, SAD can affect your mood, sleep, appetite, and energy levels, taking a toll on all aspects of your life from your relationships and social life to work, school, and your sense of self-worth. You may feel like a completely different person to who you are in the summer: hopeless, sad, tense, or stressed, with no interest in friends or activities you normally love. While a less common form of the disorder causes depression during the summer months, SAD usually begins in fall or winter when the days become shorter and remains until the brighter days of spring or early summer.
SAD affects about 1% to 2% of the population, particularly women and young people, while a milder form of winter blues may affect as many 10 to 20 percent of people. Since the amount of winter daylight you receive changes the farther you are from the equator, SAD is most common in people who live at least 30 degrees latitude north or south (north of places such as Jacksonville, Florida, Austin, Texas, Cairo, Egypt, and Hangzhou, China, or south of Perth, Australia, Durban, South Africa, and Cordoba, Argentina). No matter where you live, though, or how dark and cold the winters, the good news is that, like other forms of depression, SAD is treatable.