Low-grade inflammation, reflected in the overproduction of acute-phase proteins such as C-reactive protein (CRP), pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TFN-α) has been established as a risk factor for several neuropsychiatric disorders (Giacobbe et al., 2020; Mitchell and Goldstein, 2014), including major depressive disorder (Colasanto, 2020), depression (Kiecolt-Glaser et al., 2015; Zunszain et al., 2012; Sawyer et al., 2019; Cattaneo et al., 2020; Pitharouli et al., 2021) and schizophrenia (Osimo et al., 2018). Here, IL6 is linked to major depressive disorder.