Abstract
For over the twenty years, the neutrophil-to-lymphocyte ratio has provided insight into the etiology of a host of acute and chronic health conditions. Concomitantly, skewed ratios for the absolute count of mononuclear cells to T-lymphocytes has demonstrated prognostic capability for a range psychiatric and non-psychiatric conditions. Most recently, there has been an uptick in corroboration from structural and functional neuroimaging indicators for the role of these myeloid cells in neurodegenerative and neuroinflammatory processes leading to a cluster of neuropsychiatric syndromes characterized in compromised cognitive, affective, and motor functioning. Moreover, these deficits are mostly evident in setting of acute and chronic disease comorbidity implicating aging and immunosenescent processes in the manifestation of these geriatric syndromes. The studies reviewed in this special edition implicate neutrophil and monocyte expansion relative to lymphocytopenia in the sequelae of depression, cognitive and functional decline, as well as provide support from a range of neuroimaging techniques that identify brain changes that coincide with increase in the NLR and MLR.