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Sir: Depression is a common but debilitating illness in theUnited States with a prevalence rate ranging from 4.8% to 9.2%in primary care practice.1 Fortunately, there are many antidepressantmedications to treat patients with depression. However,up to 46% of patients treated with antidepressants do notadequately respond to treatment.2 A smaller number 5% to10% will continue to experience depression despite numeroustherapeutic interventions.3 Clinicians are then left to treat thesepatients who do not experience a full response using a numberof treatment options.