Seasonal Affective Disorder (SAD) is a type of depression in which symptoms are more severe in the winter. It is sometimes called the “winter depression” for this reason, although it is not uncommon for symptoms to start to appear in autumn as the days get shorter. What Causes SAD? Experts are not entirely sure what causes SAD but there are a few theories that have been put forward. The main theory is based on the effects of lack of sunlight on the body, particularly the prod