Major Depressive Disorder affects approximately 15% of the adult population over a lifetime. Controlled studies indicate that short-term antidepressive medications or psychotherapy produce full remission in only about 46% of patients. Furthermore, about 80% of patients will continue to have subsequent recurrences after remission of the first episode, with each episode increasing the probability of future recurrences. The World Health Organization estimates that by the year 2020 depression will be the second largest cause of medical disability worldwide. As a result, there is a need to validate treatments that produce remission and prevent recurrences upon long-term follow-up. Furthermore, since several treatment types are currently widely practiced, there is a need to demonstrate both their efficacies and cost effectiveness.