Definitions of antidepressant treatment response, remission, nonresponse, partial response, and other relevant outcomes: a focus on treatment-resistant depression.

Multiple definitions have been used to characterize the outcome of treatments for depression. Beyond the simple criterion of a statistically significant improvement in depression rating scale scores, researchers have had to use more clinically relevant categorical outcomes: response (without remission), remission, nonresponse, partial response, relapse, recurrence, recovery, and, more recently, depressive breakthrough. This article reviews the definitions of these terms and their relevance for the study of treatment-resistant depression.