Depression is second only to hypertension as the most common chronic condition encountered in general medical practice (at least one in ten outpatients has major depression). Depression should not be viewed as a mood. Sadness is a mood. Depression is a disorder in which the individual loses the emotional flexibility to respond to what is happening in their world.
Completed suicides account for 30,000 deaths in the US per year. Only about half of people who complete suicide are significantly depressed at the time they do it. The greatest predictor of completed suicide is the previous history of a suicide attempt.