The biological face of melancholia: Are there any reliable biomarkers for this depression subtype?

Background: Melancholic depression (MD) is a subtype of Major Depression associated with more clinical severity and poorer prognosis that non-melancholic depression (NMD). The differentiation between depression subtypes is still clinical, although the identification of specific biomarkers could be useful for diagnosis and the development of new treatments. Purpose of the present manuscript is to review the biomarkers that have been associated with MD. Methods: We performed a bibliographic research on the main databases (PubMed, Embase, Psyclnfo, Isi Web of Knowledge, Medscape, The Cochrane Library), in order to find studies that proposed biological markers for melancholic depression. A total of 14 studies ma our inclusion criteria. Results: Most of studies focused on immune dysregulation. Subjects with MD show biological abnormalities than healthy controls (HC). MD might be characterized by specific biological changes and it could be associated to more severe abnormalities with respect to NMD; however especially about this latter point the available data are preliminary. Limitations: Most available data have not been replicated; the studies focused on different biomarkers. In addition, many articles report results on a limited sample size. Conclusions: Melancholic depression is a subtype of major depression that seems to be associated with specific alterations of different biological systems. Future studies with larger sample can confirm the results and hypothesis presented in this review.