IL6 and major depressive disorder: IL-6 is increased in human serum, cerebrospinal fluid (CSF) and post-mortem brain tissue in multiple psychiatric disorders including SZ, ASC, BD and major depressive disorder (MDD) (Gandal et al., 2018, Khandaker et al., 2014, Lu et al., 2019, Perry et al., 2021, Sasayama et al., 2013, Schwieler et al., 2015, Zhao et al., 2021).