Peripheral inflammatory markers in melancholic versus non-melancholic depression

Background: Peripheral inflammation has been associated with major depression, however there is a paucity of studies examining whether inflammatory profiles differ across depressive subtypes. The current study sought to compare peripheral inflammatory markers in patients with melancholic versus non-melancholic depression and with healthy controls. Method: Eighty outpatients with a current major depressive episode (MDE) were assigned as having a melancholic or a non-melancholic depressive subtype based on clinician diagnosis and the Sydney Melancholic Prototypic Index (SMPI). Participants provided peripheral venous blood from which plasma levels of cytokines and other inflammatory markers (C-reactive protein (CRP), neutrophil/lymphocyte ratio, plasma cytokines) were compared across the two patient groups and also to a group of 81 age-matched healthy controls. Results: Patients with melancholic and non-melancholic depression demonstrated increased CRP and decreased interferon-gamma (IFN-gamma) levels compared to controls. Using clinician diagnosis of subtype, interleukin-12 (IL12) and interleukin-10 (IL-10) levels were elevated in melancholic patients versus non-melancholic and control groups, with no differences found for the other measured markers of inflammation. Conclusion: Study findings demonstrate shared inflammatory changes across certain inflammatory markers (CRP and IFN-gamma) and increases in IL-12 and IL-10 levels specific to melancholic depression. While generally supportive of previous work, our peripheral inflammation findings in melancholic depression are relatively novel and suggest this subgroup may benefit from anti-inflammatory therapies. Further studies are required to replicate these findings.