In 1990, over 11 million people in the United States suffered from major depression, which annually cost the nation 44 billion dollars.

Thus, the treatment of major treatment of major depression is literally a billion dollar industry. Surprisingly, little research has been done on the effectiveness of the different treatments for depression.

The best way to scientifically evaluate the effectiveness of therapy is to conduct a randomized controlled clinical trial. In these trials, patients are randomly assigned to treatment and control groups. Both the patient and the investigators are kept “blind” as to whether the patient is in the treatment or control group. Usually the control group receives a placebo (inactive) therapy. The clinical trial then waits to see if the treatment group does better than the control (placebo) group.