IL1B and major depressive disorder: The IL-1-type cytokines are major mediators of neuroinflammation and accumulating evidence suggests that IL-1β is a key contributor to neuronal deterioration in depression (Maes et al., 2012; Fernanda et al., 2017) Levels of IL-1β are increased within the brain in response to chronic stress (Pan et al., 2014) and inhibiting IL-1β reversed stress-induced social avoidance in rats (Ramirez et al., 2015).