Translating clinical science into effective therapies.

Identifying a patient with treatment-resistant depression involves ensuring that at least 2 evidence-based antidepressant trials from two different pharmacologic classes have been undertaken and determining their impact on patients' symptoms, functioning, quality-of-life and social relationships as outcomes. When assessing depressive symptoms throughout the course of treatment, clinical judgment should be supplemented by using standardized tools such as the 9-item Patient Health Questionnaire (PHQ-9) and the Quick Inventory of Depressive Symptomatology (QIDS). Adjunctive treatment strategies preserve the benefits of first-line antidepressants in partial responders and potentially enhance the initial antidepressant's effect through complementary mechanisms of action. Novel "multimodal" pharmacotherapies with diverse potentially beneficial mechanisms of action are in development, which have varying degrees of activity across multiple monoamine systems including those regulated by serotonin, dopamine, and glutamate.