True depression--mental illness--is not just the blues or a bad day. It is a chemical illness that can have tragic results.About one in 10 americans suffers some form of depression, according to the national institute of mental health.Depression has devastating effects on a person's relationships with family and friends, on the ability to do productive work, and, of course, on the ability to enjoy life.When professionals use the word "depression," they're referring to an illness that deserves care and treatment.