A study using data from a longitudinal naturalistic cohort study focussed on atypical versus melancholic depression as two differential subtypes of MDD which were classified by the clinician-administered Composite International Diagnostic Interview (CIDI), and showed atypical depression was associated with increased CRP, IL-6 and TNF-α in comparison to melancholic depression and healthy controls (Lamers et al., 2013). This evidence concerns the gene IL6 and major depressive disorder.