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 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.