IL6 and depressive symptom measurement: An increasing number of studies have demonstrated that elevated levels of plasma IL-6 and CRP levels are associated with an increased risk of depression (Liu et al., 2014; Wium-Andersen et al., 2014), and can even predict subsequent depressive symptoms (Valkanova et al., 2013), although no significant correlation between IL-6 or CRP and depression has also been reported (Chocano-Bedoya et al., 2014).