A depressive disorder is not a passing blue mood but rather persistent feelings of sadness and worthlessness and a lack of desire to engage in formerly pleasurable activities. A complex mind/body illness, depression can be treated with drugs and/or therapy.
A depressive disorder is an illness that involves the body, mood, and thoughts. It interferes with daily life, normal functioning, and causes pain for both the person with the disorder and those who care about him or her.
A depressive disorder is not the same as a passing blue mood. It is not a sign of personal weakness or a condition that can be willed or wished away. People with a depressive illness cannot merely “pull themselves together” and get better. Without treatment, symptoms can last for weeks, months, or years. Depression is a common but serious illness, and most people who experience it need treatment to get better. Appropriate treatment, however, can help most people who suffer from depression. (Psychology Today)