Depression is a mood disorder that causes a persistent feeling of sadness and loss of interest. It affects how you feel, think and behave, and it can lead to emotional and physical problems.
Depression and pain are closely related. Depression can cause pain, and pain can cause depression. Sometimes pain and depression create a vicious cycle where pain worsens symptoms of depression and the resulting depression worsens feelings of pain.
In many people, depression causes unexplained physical symptoms, such as back pain or headaches. This kind of pain may be the first or the only sign of depression.