For example, the relationships between venous blood levels of IL-6, CRP and depression have been weaker in studies using self-reported instruments rather than clinical diagnosis to ascertain depression, in community-based subjects compared to clinical samples, and when participants treated with antidepressants at the time of immune assessment have been included in the analysis (Hannestad et al., 2011; Hiles et al., 2012a,b; Howren et al., 2009). This evidence concerns the gene IL6 and major depressive disorder.