Treatment-resistant depression: additional perspectives

Treatment-resistant depression (TRD) is usually thought to characterize -10-15% of patients who are refractory to all conventional antidepressant therapy. However, in its broadest definition, TRD occurs across a spectrum of severity and is not an uncommon clinical problem, defining a sizeable portion of patients with mood disorders. Although the majority of treatment outcome studies report response rates to antidepressants in the 60-70% range, this figure should not be viewed as indicating the rate of remission, but rather an estimate of improvement from minimal response to complete remission. Thus, while as many as 60% of depressed patients may have some degree of response to antidepressant treatment, only ~ 25-30% of patients will achieve clinical remission. Therefore, estimates of response rate can hide the fact that most patients who are described as 'improved' with pharmacotherapy actually have a form of partial TRD. In this framework, a more realistic view of the TRD syndrome should encompass a broad spectrum of cases ranging from partial to complete drug resistance. It is in this context that we view this timely review on TRD by Malizia and Bridges.