DEPRESSION Depression is the main cause of disability Trusted Source worldwide, according to the World Health Organization (WHO). It can affect adults, adolescents, and children. Definition: A person with depression may experience persistent sadness. Depression is a mood disorder that involves a persistent feeling of sadness and loss of interest. It is different from the mood fluctuations that people regularly experience as a part of life. Major life events, such as bereavement or the loss of a job, can lead to Trusted Source depression. However, doctors only consider feelings of grief to be part of depression if they persist. Depression is an ongoing problem, not a passing one. It consists of episodes during which the symptoms last for at least 2 weeks. Depression can last for several weeks, months, or years. Signs and symptoms The symptoms of depression can include: a depressed mood reduced interest or pleasure in activities once enjoyed a loss of sexual desire ...