Its more subtle than that. Left untreated, it grows from a subtle feeling of unease, and slowly becomes more pervasive in one's character. Eventually it can lead to a variety of different behaviors, up to and including suicide. Depression is an illness that affects the entire body, not just the mind. Depression is an illness that one in five people will suffer during their lifetime.
Depression is the leading cause of alcoholism, drug abuse and other addictions.
Depression is an illness that can be successfully treated in more than eighty percent of the people who have it. Women, however, suffer from depression twice as much as men do. At least half of the people suffering from depression do not get proper treatment. Untreated depression is the number one cause of suicide. Depression is second only to heart disease in causing lost work days in America.