How can depression work?

Bain Chemistry: Depression is a medical illness that involves the mind and body. Also called major depression, major depressive disorder and clinical depression, it affects how you feel, think and behave. Depression can lead to a variety of emotional and physical problems. You may have trouble doing normal day-to-day activities, and depression may make you feel as if life isn't worth living.

Persistent despair: Can begin a downward spiral. As energy & motivation decrease, people often withdraw, isolate themselves & feel helpless & hopeless. They may become self-critical & self-blaming. Behaviors, thinking & emotions intensify each other. Chronic, moderate depression is dysthymia. Research & clinical experience show that cognitive-behavioral therapy (cbt) is the most effective treatment.