Blood-based biomarkers in depression: emerging themes in clinical research.

There is growing interest in identifying blood-based biomarkers for depression. This brief review examines recent research in this area, using a focused literature search to identify emerging themes in current work pertaining to major depressive disorder (MDD). The results suggest that biomarker-based research in MDD is still in its relative infancy and is focused on answering two major questions: what biomarkers reliably distinguish individuals with MDD from those without MDD; and what biomarkers can identify or predict treatment responders versus non-responders? However, a number of issues limit the potential utility of positive findings in each case; chief among these is the lack of truly independent replication cohorts in which to validate initial findings. Some promising results have emerged pertaining to predictors of antidepressant effectiveness and, if validated by future independent studies, these may hold promise as targets to be developed within clinical settings and may ultimately guide treatment regimens for patients suffering from MDD.