IL6 and major depressive disorder: Although the linear relationship between BDI-II depression and IL-6 diurnal index slightly failed to survive the Bonferroni correction, we also compared depressive individuals defined by the BDI-II cut-off score (n = 12) and non-depressive ones (n = 96) with ANCOVA controlling for age, sex, sleep duration, and BMI, in consideration of a possible non-linearity of biomarkers as suggested in the allostatic load model (1).