INVESTIGATING NEURO-INFLAMMATION AS A KEY CONTRIBUTING FACTOR IN THE DEVELOPMENT OF DEPRESSION

Abstract

Depression is a complex psychiatric condition that negatively impacts mental health worldwide and this study examines the role of neuro-inflammation in the onset and progression of depression. Depression is now known to be a neurotransmitter imbalance disorder and also a systemic disorder with immune dysregulation and chronic low-grade inflammation. However, despite the development of psychopharmacology, there still exists a significant number of partially responsive or treatment-resistant patients with Major Depressive Disorder (MDD) that cannot be fully explained by the monoamine-based models. This underscores the importance of investigating the neuro-inflammatory pathways as a possible underlying biological mechanism affecting depressive pathology. The study is based on the neuroimmune hypothesis of depression that states that peripheral immune activation results in an increase of pro-inflammatory cytokines (IL-6, TNF-α, CRP), which leads to impairments in neuroplasticity, functioning of the hippocampus, and regulation of the hypothalamic-pituitary-adrenal (HPA) axis. A mixed design methodology was used with systematic review and secondary quantitative meta-analysis. Clinical data were taken from 18 peer-reviewed clinical studies, and a pooled sample of 4200 patients with MDD and 3800 healthy controls from psychiatric hospitals and psychiatric research databases (2015-2025). Effect size comparison, correlation analysis and multivariate regression modeling were performed to analyze statistical data. Results showed that the inflammatory biomarkers in depressed individuals were significantly higher (p < 0.01). There was a significant positive correlation between IL-6 and symptom scores (r = 0.62), and a correlation between TNF-α and cognitive impairment measures. The anti-inflammatory adjunct treatments proved effective with a statistically significant 28% decrease in HAM-D score and a 21% decrease in CRP level.