Depression range from lasting feelings of unhappiness and hopelessness, to losing interest in the things you used to enjoy and feeling very tearful.
There can be physical symptoms too, such as feeling constantly tired, sleeping badly, having no appetite or sex drive, and various aches and pains.
The symptoms of depression range from mild to severe.
At its mildest, you may simply feel persistently low in spirit, while severe depression can make you feel suicidal, that life is no longer worth living.
Most people experience feelings of stress, unhappiness or anxiety during difficult times.
A low mood may improve after a short period of time, rather than being a sign of depression.