This is supported by observations of elevated levels of pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα) in people who suffer from chronic major depression (Dowlati et al, 2010; Müller and Schwarz, 2007; Young et al, 2014) and observations of neuroinflammation in patients with bipolar disorder (Rao et al, 2009; Stertz et al, 2013; Yüksel and Öngür, 2010) and schizophrenia (Garver et al, 2003; Rosenblat et al, 2014). Here, IL6 is linked to bipolar disorder.