This study involves a naturalistic follow up of responders from the study entitled "Integrated biological markers for the prediction of treatment response in depression", or the CAN-BIND-1 study. In addition, this study is also open to other participants who completed other CAN-BIND studies, as well as remitters who meet the inclusion criteria. Since patients usually seek medical attention only after relapse has occurred, imminent precursors to relapse are not well known. In this study, participants who are currently responding to an oral antidepressant treatment regimen and/or therapeutic intervention will be monitored over a minimum period of 13 months, which provides a unique opportunity to discover near-term biomarkers of relapse.