Is immune activation simply a non-specific marker of depression severity or chronicity or does it indicate an underlying pathophysiological path to depressive or other mood disorders?

Abstract

In both population-based and clinical cohorts, cross-sectional and longitudinal studies have reported associations between a range of non-specific markers of immune activation (e.g., pro-inflammatory cytokines) or chronic inflammation (e.g., C-reactive protein [CRP]) and depressive and other mood disorders (Dowlati et al. 2010; Hickie et al. 2018; Khandaker et al. 2017; Orsolini et al. 2022; Valkanova et al. 2013). The clinico-pathological significance, and directional relationships, of these associations tended to be downplayed as the systemic levels of these inflammatory markers were not in the ranges typical of active infective, inflammatory or significant autoimmune diseases.