IL6 and major depressive disorder: Study 1 also includes as secondary outcomes immunology [inflammatory biomarkers formerly associated with depression and anxiety (e.g. CRP, IL-6 and TNFalpha); biomarkers of the development of effective immune surveillance (e.g. IFNgamma, IL-12/18, GM-CSF); suppressive cytokines that may block the development of effective anti-tumour immune responses (e.g. IL-10, IL-4/13)] and epigenetics markers [expression of miRs associated with stress response, inflammation or BC prognosis (miR-21, miR-146a, miR-155 and miR-Let7)].