IL6 and major depressive disorder: Longitudinal analyses of the data have also shown that serum IL-6 at age 9 years predicted depression symptoms of diurnal mood variation, concentration difficulties, fatigue, and sleep disturbances at age 18 years (Chu et al., 2019), however, after controlling for confounders, there was no association between CRP at age 9 years and depression symptoms at age 18 years.