feeling of sadness and a loss of interest in the activities a person usually enjoys."depression! facst and solutionsDepression, as defined by the World Health Organization, is "a disease characterized by a constant feeling of sadness and a loss of interest in the activities a person usually enjoys." If you develop these symptoms on a daily basis for two weeks, you are depressed: loss of desire to do activities, weight and appetite change, sleep disturbances, feeling tired, decreased activity, and lack of focus. There are more than 300 million people of all ages worldwide who suffer from depression. The World Health Organization says it is the leading cause of disability globally.