Although inferences related to inflammatory states and TSPO should consider that TSPO expression is not unique to microglia and that elevated TSPO binding in humans could also be attributable to local proliferation of myeloid cells or increased recruitment of monocytes (Narayan et al., 2017; Owen et al., 2017), TSPO remains the most widely used marker of inflammation in the living brain in diverse studies of neuropsychiatric disorders, including MDD (Mondelli et al., 2017; Enache et al., 2019). This evidence concerns the gene TSPO and major depressive disorder.